Hi guys,
Just an update on this situation.
It's still doing it.
I'm thinking of trying to flash/upgrade the BIOS as the last option. I've tried numerous drivers, a clean XP install and it's just not working. I don't think it's a temperature problem becuase it happens at completely random times - for example the other day it happened just after I'd turned the machine on!
Trouble is, the instructions you get in the MSI folder are just too confusing!
Can anyone give me a basic outline of what I need and what I have to do? I wish there was an application which you could just run and it would do it for you

It's an MSI P6N SLI V2 with American Megatrends Inc BIOS V02.61.
Thanks!