Is your PC getting toasty? Is your CPU getting charred and your motherboard melting? Okay, I'm exaggerating, but if your components are reaching a potentially damaging temperature, Motherboard Monitor can let you know. This free program monitors and reports on the temperatures inside your PC case using the built-in sensors on the processor and motherboard. If things get too warm, it can sound an alarm and automatically shut your PC down before anything gets damaged.
It's a great tool if you build your own PCs because it can tell you if your system is overheating due to insufficient ventilation. It can also monitor the voltages that your power supply is outputting, warning you if they fall below a certain level. In these days of power-hungry graphics cards (sometimes in pairs with up to four GPUs) and the practice of loading a case with drives, an overextended power supply can lead to crashes and data loss, so it's good to know that the power supply is up to the job.
However, it doesn't work with all motherboards: Some won't report back a temperature, and the author stopped updating the program in 2004. But it's still useful for anyone who has built their own system, or who has added components to their system and is concerned about how hot they get.