Computer Constantly freezing up.

[Malcolm]

I recently helped my uncle out with his PC, when i got it, the Video card was toast and the fan on the CPU heatsync was broken. The reason he got me to look at his PC in the first place is because it was freezing. Now i got him a new video card(x1600 pro AGP) and a new heatsync for his CPU(AMD 64 3000+ S754) and now the computer is freezing more than it was before. Now i checked the video card and it works in another PC and i am pretty sure i have the latest drivers. I think it may be a PS issue, but im not really sure, and i dont want them to spend more money unless i am 100% sure.
Any ideas would be great.
Thanks

 

[mkaibear]

Reinstall windows. succinct, but good!

 

[evongugg]

Test the memory with Memtest86.

 

[rcs2749]

Try a new power supply.

 

[ilias]

also check the hdd. some ppl dont think about it very much but a damaged hdd means that windows crash (or stop responding for 15 sec and then continues as nothing happened) when it cant access something vital from the hdd (page file or system files).