Windows XP Reboots for no reason

[ToddD]

Ok, I know my OS (Windows XP Home) isn't the desired version, but it has always worked great and suited my needs perfectly. Recently, I upgraded my processor from a 2.26 to a 2.66 ( got the new one from a working system) and on the advice of a friend I updated my system BIOS from version A07 to P13. I got the new BIOS from the Dell site. Now after using the computer for about 3 hours it reboots on it's own while I play World of Warcraft or do anything intensive. What I want to know is if the problem is the new BIOS of if the problem could be heat related with the new processor. There seemed to be a good amount of heat sink compound already on the new processor and on the heat sink. My computer is a Dell Dimension 8200.

[venney]

i dont know if this is directly the case, but i think you are supposed to put a new layer of thermal compound on the cpu when you install it.

[liljim]

venney is right, cpu and heatsink need to be cleaned off and apply a new thin layer of thermal compound.

[ToddD]

Ok, I removed the heatsink, cleaned the old compound off the processor and heatsink, applied a thin layer of Arctic Silver 5 and re-installed. I booted up the system and let it sit and warm up for about a half hour. When I returned, I surfed the net for about a half hour and had no rebooting problems. Then i started World of Warcraft and played for approx. 45 minutes. Everything seemed okay, then out of nowhere the system rebooted. Needless to say I was a bit angry. I'm now wondering if the problem could be in the updated BIOS I flashed. I even re-flashed the new BIOS. I think doing the BIOS update was a big mistake. Can anybody tell me if there is a way to maybe clear the bios and start from scratch? The original BIOS (version A07) never gave me any problems and I now believe the friend who recommended I update is an idiot. Maybe I am too for not knowing any better.....
Any help would be GREATLY appreciated.

[liljim]

[Psymon]

rebooting sounds more like the GPU failing than the CPU.

When the pump for my watercooling died, my pc would shut down.
when the fan on my dad's GPU died, the pc would restart.

I'd say do what liljim suggests, downloading speedfan.
After installing this you'll be able to see the temperature of the components in your PC.
one should be labeled CPU and another, GPU. (it did this for me)

However, I'd recommend running a game in a window instead of fullscreen, like WoW, and keep an eye on the temperatures.
I find it's easier to see what the temperatures are like using the 'graph' tab in speedfan.