There seems to be a lot of information on the web about this and currently I'm confused as to what I should do next. The PC is brand new (Oct 2006) it's a Zoostorm top of the range one (Dual core, Nvidia 7900gtx, creative labs xfi soundblaster platinum etc). I don't have much loaded on it. I've got F-secure (internet security), XP home, MS office 2003 and so far games such as FEAR, Prey, BF2142, Unreal Tournament 2003, and a few Star wars games for my boys. The symptoms seem to be that it randomly reboots whilst playing games. Sometimes it's fine whilst other times it will suddenly reboot. It's usually in the first 5-10 minutes after starting. Once it's done it (maybe a few times) it then seems to settle down and is fine. I've loaded the latest drivers for the sound and graphics card, I've run memtest (and found no memory problems). Does anybody else have any suggestions?
Have you looked in the event viewer to see what is happening when it reboots?. Right click My Computer/click Manage/click event viewer, and look under applications & system. Look for any red marks/if you then right click the entry/click properties, and you will be given information about the fauly, also if you click on the microsoft URL it will give you more information.