I've been having some real problems in XP, with high system instability especially during games. I tested the memory and that seems okay, and I don't think it's a heat issue. I'm running an Athlon 2100 on a VIA KTS400. I think I may have stumbled upon something significant:
When I was setting up my computer from scratch, it would freeze up when I tried to install XP and display a blue screen saying something to the effect of "IRQL_NOT_LESS_OR_EQUAL." I had no idea what this meant, but it went away once so I continued with my install -- I suppose this problem did not fix itself (damn!), because when I tried to reinstall windows yesterday, it is doing this again -- I imagine that whatever this error is, THIS is what is causing windows instability, but XP must be helping cover the crash, because I don't get a blue screen or the same error but merely application crashes. Any ideas?
Also, when mounting my motherboard, I used the little cardboard washer things that came with my case ...are these for the motherboard mounting or not? I know that improper mounting can lead to problems.
Alot of windows "blue screen" error messages are caused by memory compatibility issues. You can try using the spd setting for memory, or even lowering your cpu fsb and see if that helps. What type and brand of memory are you using? Also, what brand and rating of power supply do you have?