At one time, there was only Windows and only one Windows, Windows v3. Now there are Windows, plural: Windows 95, Windows 98, Windows NT, Windows 2000, and Windows Me. What's more, the possibility exists that you, as a power user, have more than one copy of Windows -- or more than one type of Windows -- on one machine.

Having multiple installations of Windows on one computer is called dual booting or multiple booting. Windows NT and 2000 are designed to be installed in conjunction with other operating systems, especially Windows 95/98/Me. Windows 95/98/Me are not: When you install them on a PC, they want to be the only OS on that PC.

Is there any way around this? Yes; in fact, there are many possibilities. This article will step you through how to get the various versions of Windows to coexist with each other on the same PC.  Over the years, Windows has grown slightly more tolerant of having more than one installation of itself in a given PC -- especially NT and 2000 -- but a number of scenarios aren't supported at all by Microsoft and require a little coaxing or, in some cases, trickery.

You can take several paths to achieve multiple booting. These depend on what's already installed in your computer, how many hard drives and partitions you have, and whether or not you're amenable to (or capable of) using third-party programs to control boot choices. If your machine is sufficiently powerful enough (500MHz or better and at least 128MB of RAM), you also have the option of using an emulation system such as VMware to run your other OSes.

First, you need to verify which OS you're currently running, and which OS you want to add to your system. If you're adding Windows 95, 98, or Me to a machine running Windows 2000 or Windows NT, that's the most complex scenario. Because it's also the scenario about which we've received the most correspondence from our readers, we'll address it first.

Adding Win NT or 2K to a machine running either Windows 95, 98, or Me is actually much easier, because both NT and 2K are designed to coexist to a high degree with other operating systems. Some pitfalls may be in store, but we'll cover them in the following pages.

Install 95/98/Me on a NT/2000 PC

Installing Windows 95, 98, or Me on a Windows NT system is probably the most difficult of the scenarios listed here. The reason is fairly simple: Windows 95/98/Me wants to be the only OS on a given computer, and will take steps to insure that nothing else can boot up.

If you have Windows NT already installed on the computer (on a FAT partition), for example, you'll get a warning during the Win95/98/Me installation process about the presence of NT system files. If you have an NTFS partition, Win95/98/Me will report it as being damaged and won't let you do anything about this except abort the installation, since it doesn't let you interactively repartition your disk during setup.

If you have NT/2K on a FAT partition and install Win95/98/Me on it anyway, any NT/2K boot files will be erased, and the boot sector will be replaced with a Win95/98/Me edition. Win NT/2K, however, has repair tools to address this problem, which we'll discuss in detail later.

Here are the steps for adding a Win95/98/Me installation to a Windows NT machine.

1. Ensure your NT PC has Service Pack 6a.
Windows NT, in an out-of-the-box installation, has problems that can cause serious disk corruption if you're using a drive larger than 2GB (and who isn't these days?). Before doing anything else at all, make sure you have patched the system with the latest Windows NT Service Pack plus whatever hotfixes are relevant to your computer. With Windows 2000, you can patch with Service Pack 1, but it's not required, since it comes 95/98/Me-aware out of the box.

2. Make a Windows NT/Windows 2000 repair disk.
Repair disks in Windows NT/2K are floppies, created with a system utility, that contain copies of key Registry entries as well as a description of the partition geometry of the disk. If either of those things gets damaged, you can rebuild them to an extent. A repair disk is one of those underrated Win NT/2K features that can often save you when you least expect it. If you make a mistake during this process, you won't regret having it.

To build a repair disk in Windows NT, use the RDISK.EXE command-line utility. Just run it and follow the prompts. In Windows 2000, run the Backup utility and click the Emergency Repair Disk button on the Welcome tab.

3. Prepare a FAT partition.
Windows 9x can't install onto anything other than a FAT or FAT32 partition. FAT, also referred to as FAT16, is the original partition format used by DOS and, later, Windows 95. Windows 98 introduced FAT32, a revised version of FAT that could support bigger partition sizes and was more reliable. But NT supports only FAT, so you need to have a FAT partition with enough free space for Windows 9x to be installed. FAT32 cannot be read or written by a Windows NT machine.

To be scrupulously honest, it's possible to have Windows NT read and write FAT32 partitions with a third-party utility. However, if you want your system to be as reliable as possible, we don't recommend using such a method.

 

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	Only FAT16 or FAT32 partitions, not NTFS, can support a Windows 95/98/Me installation. FAT16 provides the best cross-compatibility with other operating systems.

The partition in question doesn't have to be the primary boot partition in the computer, but it must be a DOS-accessible partition for the installation to succeed, and the bootable partition in the system must be FAT. If there's no such spare partition in the system, you will have to make one using a third-party tool such as PartitionMagic. Windows doesn't support the selective editing of partitions and neither does Windows NT, for that matter!

You can use the same partition that holds Windows NT itself, but we don't recommend it for two reasons:

1) You must not use the same directory name for both operating systems. This actually varies by default: NT installs in \WINNT, and Windows 9x installs in \WINDOWS. However, if NT were installed in \WINDOWS for whatever reason, it would create problems, and some applications stupidly expect Windows to be installed in \WINDOWS and nowhere else.

2) The \Program Files directory is used by both operating systems to hold apps that are installed by default -- everything from IE to Solitaire. Because some of these apps are OS-specific -- some are specifically for NT that aren't for 9x and vice versa -- you may wind up breaking one OS's default app set if you install it on top of the other. This alone is reason not to install both OSes on the same partition, since the \Program Files directory can't be easily redirected during the install process.

Preparing a partition in Windows NT is done through the Disk Administrator utility. Right-click in the listed free space on a drive and choose Create; right-click in the same space again and choose Commit Changes Now; then Format.

4. Create a Windows 9x boot floppy.
Sure, you're always supposed to have a boot disk handy, but more often than not, you don't. For dual booting, you'll definitely need a Windows 9x boot floppy disk. Find a PC running Win9x and a blank floppy disk. You'll be preparing a bootable floppy disk that will have nothing on it save the command-line version of Windows, which is basically, DOS. To do this, boot Win 95/98/Me and run the following command-line operation: FORMAT A: /S with a blank floppy in drive A:.

From the \Windows\Command directory, copy the SYS command to the A: disk as well.

NOTE: Don't mix and match OSes here. If you're installing Windows 95, don't use a Windows 98-prepared boot disk. It won't work. Windows 95, 98, and Me all practice pretty stern revision control over their own internal files and utilities.

5. Copy Win98 installation files onto the hard drive.
With Win NT running, insert the Windows 98 CD-ROM and copy the contents of the \SETUP folder onto an available FAT partition. Use the same folder name unless a folder named SETUP is already there. If it is, try a folder name such as NewSetup.

6. Boot with the floppy; then run the install files from hard drive.
Put the prepared boot floppy in your A: drive and reboot. Once you've booted into command-line Windows (DOS mode), type "SYS C:" to transfer the boot files. The command should return the statement "System transferred."

Switch to the \SETUP folder you copied over and run SETUP.EXE. Windows Setup should begin the install process.

As we mentioned before, you're going to get a warning about Windows NT system files being present (or a generic warning about files from another OS, depending on what else may be in your computer) when you go through the install process. Ignore this for now, as we'll be back later to take care of it.

The installation process for Windows 98 should not vary greatly from the way you would normally set it up. The one major difference needs to be the location of the Windows installation; it can't be on the same partition with your NT install, or your \Program Files folder will contain inconsistent copies of some programs.

Once the installation finishes, make sure your system boots correctly into Windows 98 before continuing. If Windows 98 refuses to boot, unrepaired disk problems may have occurred during Setup.

7. Repair your Windows NT boot files.
Once Win98 is in and running, the last step is to repair the Win NT/2000 boot files. This will allow you to use the NT boot loader to choose between NT/2K and Windows 9x.

Repairing the boot files is fairly automatic. Boot the Windows NT/2000 setup disks -- or the CD-ROM, if you can boot CD-ROMs -- and select R in Setup to repair. Choose to repair only the Windows NT boot sector -- nothing else. Note that if your Windows NT/2K installation can't be found, you should pop in the repair disk you made (you DID make one in step 2, correct?) and use that to help the repair program find your installation.

Once the repair operation is finished, boot the computer to see whether you get the Win NT/2K boot options menu with a new entry at the bottom for Windows 9X. Usually you will. If not, you'll need to add a line to the file BOOT.INI, which should be a read-only file in the root directory of your boot drive. You'll need to modify the file's permissions so that it's not read-only in order to change it.

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	Editing the BOOT.INI file is easy enough -- use Notepad or another plain-text editor -- but you'll need to turn off the file's read-only attribute before you can save it. Also be careful not to edit anything except the reference to Windows 95/98/Me

Add the line:
C:\="Windows 95"

to the bottom of the BOOT.INI file, and reboot. The comment in quotes can be anything you like, as long as it's distinct from the other menu choices.

The next time you reboot your system, simply choose the appropriate selection from the boot menu to boot either Win 95/98/Me or NT/2K.

Install NT on a Win2000 PC

Adding Win NT to a Win2000 PC should in some ways be treated like adding Win95/98/Me to a Win NT/2000 installation. The main reason for this is, on the whole, that NT cannot recognize Win2000 NTFS partitions (unless you have Service Pack 6A, and even then it seems to have problems). Win2000's edition of NTFS contains some features, such as changes to how permissions work, that are not entirely backwards-compatible with WinNT. The best thing to do is place NT on a separate partition, where it can use its own version of NTFS.

You'll also need to repair Win2000's boot files, just to be safe. The process for doing this is identical to the repair process in Windows NT.

Install NT/2000 on a 95/98/Me PC

Adding Windows NT or Windows 2000 to a machine that already has Windows 95, 98, or Me on it is much simpler than the reverse for one simple reason: Windows NT/2000 is smart enough to detect the presence of another operating system during installation and modifies its boot files accordingly. Because of this, if you install WinNT/2000 in a machine that already has another version of Windows on it -- and it doesn't matter what version -- you'll see an entry in the boot manager for both editions of Windows.

The installation procedure to follow when adding NT/2000 to a 95/98/Me computer isn't enormously different from installing NT/2K in general. There are, however, a few guidelines to follow.

1. Do not install NT on a FAT32 partition.
This is probably the single most important rule. NT supports only FAT and NTFS, not FAT32, and can't be installed on a FAT32 partition. In fact, it generally can't even read FAT32 partitions. So if you're planning to make data readable by both operating systems, be sure not to place it on a FAT32 partition. Place shared data either in a FAT partition or on a networked drive.

Also, do not convert a FAT16 partition that has NT installed on it. Converting a partition with NT installed on it to FAT32 will render it unbootable.

The sole exception to this rule is with Windows 2000. Win2K can read and write FAT32 partitions without problems. Installing Win2K on a FAT32 partition, however, means you won't be able to use NTFS security features on your system partition.

2. Don't use disk compression.
In fact, this is a global rule: Never use disk compression on any multiple booting system. It's not worth it, and it creates more problems than it solves. Most drives today are big enough that disk compression is contraindicated, anyway. Windows Me won't even install onto a system that has disk compression running.

3. Do a disk check before an installation.  Lingering disk errors can cause terrible problems later on down the line when you install an operating system. During Windows installation, there's a disk check; don't skip this step.

4. Always use a discrete partition for other operating systems.  As with installing Win 95/98/Me on an NT/2K system, this rule also applies here, and for the same reasons. Installing one Windows application set over another can cause horribly unpredictable things to happen. In most cases it will break IE and Outlook Express, and if shared .DLLs are overwritten, it may cause other apps to malfunction, too.

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Each operating system should always reside on its own partition for the best possible results. Here, a FAT32 partition has been prepped for a new installation of Windows Me.

If you want to share applications between operating systems, the best way to do this is to install the app on one OS, boot the other OS, and then reinstall it into the exact same folder. However, a few applications may not work correctly if you do this: for instance, any application that uses CTL3DV2.DLL or CTL3D32.DLL, since there are discrete versions of those .DLLs for 95/98/Me and NT/2K. Your safest bet is to install apps in separate partitions, although a few programs can be coaxed into running without being reinstalled.

Another thing to be aware of when adding a new partition to a Windows 9x machine is how Windows 9x translates partitions as drives. In some cases, if you add a partition, you may break your drive-lettering scheme and possibly render your Windows 9xsystem unbootable.

Here's an example of this: On a computer that had two primary partitions, C: and D:, I had Windows NT on C: (which was marked as bootable) and Windows 98 on D:. When I added a third, logical partition, the drive lettering was thrown off and D: turned into E:, making Windows 98 unbootable.

There are two simple ways to defeat this. One is to use only primary partitions (a maximum of four per hard drive) and to add them in sequence. Another is to add Windows 9x last whenever you set up a system, to preserve the integrity of the drive mapping. The downside of this method is that it goes against the common wisdom of putting 95/98/Me on a system first, so this is recommended with some reservations. Forcing Win9x to map drives a certain way is difficult and not always successful. (Windows NT and 2000 let you map drives any way you like and are not as prone to this problem.)

Third-party Programs for Multiple Booting

Sometimes the easiest thing to do in multiple boot scenarios is to let someone else take control of the whole process. The Windows NT/2K multiple boot loader is not simple to configure and has no easy way to add operating systems that aren't directly supported. If you're booting between more than one OS, or various revisions of OSes, the boot loaders you have may not be enough to do the job.

Boot loaders work in a couple of different ways. Some of them are installed in a special partition, only a few megabytes in size that is marked as bootable. When that partition is booted, the boot loader program takes over and presents the user with a menu of possible boot choices. Usually the program analyzes the available partitions at each boot, to determine whether anything has changed since the last boot.

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System Commander works with just about any PC-based operating system to let you choose the OS you want to boot.

The best third-party boot loader out there so far appears to be System Commander from Vcom. System Commander automatically detects any changes made to your PC since the last boot and updates its menus automatically to reflect those changes.

The makers PartitionMagic also have a multiple boot manager program named BootMagic, which does many of the same things as System Commander and supports Windows 2000 as well.

VMware is another way to run multiple OSes on the same system, but without using multiple booting. Instead, VMware creates a virtual computer console on your PC -- basically, a computer within a computer. The virtual computer runs at about two-thirds the speed of your real computer and has access to many of the same resources -- disk drives, printers, network, etc. This allows you to run one or more operating systems, as many as you can devote disk space for, without having to reformat a drive partition or play around with dualboot settings.

 

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	VMware lets you run a 'virtual computer' in your computer, letting you install any operating system you choose. But it'll only work in NT or Windows 2000 and needs plenty of memory.

One main weakness of VMware is it runs only under Windows NT or Windows 2000, and it won't work in Windows 95, 98, or Me.  VMware also needs a lot of memory and processing power to get good results: On anything less than a Pentium II 400, it crawls, and it needs at least 128MB of RAM to really work well. You can try before you buy, though; the official site contains instructions on obtaining a 30-day trial license via e-mail