More Random Crash Problems

Firstly here's a full spec of my shiny new PC

AMD AthlonXP 1900+ (1.6Ghz)
512Mb PC2100 DDR RAM (NP)
Soltek SL-75DRV2 Motherboard (Via KT266A)
Western Digital 100.0Gb HD (UDMA 100)
Creative Geforce 2 Ultra
x10 DVD x 40 CD (RPC-0)
Windows XP Professional (using NTFS)

Now, I'm getting rather random system crashes, they usually happen at least ten minutes after I've turned the PC on. It crashes rather randomly, but loding a game or watching a DVD movie can often initiate a crash. These crashes are not a restart, but the system simply freezes - the screen locked, no matter what you attempt. Resetting seems the only option as ctrl alt del doesn't work.

I'd like to hear anyone's ideas on what could be making my system crash so often?

I'm wondering if the cpu is overheating? I have a cooler that should be able to cope, but (and I'm not sure if this is the cpu temp) the "temp 1" reading in the program "Smartguardian" is reading around 55oC after a few minutes of operation....is this too hot? I've no idea.


any help appreciated!