Computer freezing up

[MrBlahh]

The computer I built for my sister a few months ago is freezing up on us. The mouse and keyboard stop responding, the video stays on but is frozen and if there is any music playing it stops. Doesnt seem to freeze at any predictable time....sometimes it will be good for a while and others it will freeze up right away. Only way to get by this is to restart. It doesnt appear to be over heating since the hardware monitor that came with the MOBO says it is anywhere from about 41-45 C and her room is kinda cold. It was extrememly dusty inside with dust caked onto the side fans and in the fins of the CPU. It has frozen since cleaning it out so thats why Ive ruled out overheating. Ive checked to make sure the drivers are all up to date and they are. Im currently running Memtest86 and after about 3 hours it hasnt found any errors. Does this sound like a problem with the power supply?

Here are the computer's specs:
AMD Athlon XP 2800+
Soyo Kt-600 Dragon Plus
PNY Geforce FX 5200 (Atleast im pretty sure its the 5200)
Kingston 512 MB PC2700 Memory
The case is this thing
Nice looking case but really flimsy. It said it has an Athlon approved PSU so I thought I would give it a try.
2 optical drives:1 cd burner, 1 dvd drive and a floppy drive
WinXP Home

Any ideas of what I can try next? I thought Id ask here before we went out and spent money on a new PSU.

 

[user1234]

if her room is really cold like you say, then below freezing temps I wouldn't be surprized to see the cpu freeze out

 

[techwanabe]

How long has it been since you've done a format and fresh install of Windows?

 

[MrBlahh]

Originally posted by: user1234
if her room is really cold like you say, then below freezing temps I wouldn't be surprized to see the cpu freeze out

Probably should have said cool...her room is cool. Its been in the 40's F outside lately. We havent turned the heat on yet so her room is below normal room temperature.

Originally posted by: techwanabe
How long has it been since you've done a format and fresh install of Windows?

Probably a few months. It had windows 2000 on it originally but she wanted WinXP so I installed that.