Computer freezes

[gert74]

[Darthtanion]

Three things come readily to mind, but it could be something else. But anyway, these three problems can cause random failures:

Bad memory - download a memory testing utility to check things out
Inefficient power supply - replace with a more modern one
Cooling problems - use a temperature monitoring utility to see if this is a problem

[Yawgm0th]

The symptoms do point to hardware, but it could also be a virus of some sort.

[wayout44]

When was the last time that you cleaned the dust and fluff out of it and if you're using XP did you check the Event Viewer for any logged critical errors?

[gert74]

[bigjackusa]

Corrupted drivers can also do this. Most often audio or video drivers from my experience. I have also seen 3rd party mouse drivers do this, but usually they do it right from the start.