I have just upgraded my system to a Pentium Celeron D 2.66Ghz LGA 775 Processor with an MSI PM8M2-V LGA motherboard with 786MB of RAM and an MSI ATI Radeon 9250 128 MB DDR AGP card. Whenever I play any graphic intense game, within a few moments of loading the game, the computer simply shuts off. I am using Windows XP SP2. The problems doesnt occur in low graphics game or while using computer for office work or browsing even when being used for hours.
I have tried another card, the MSI Geforce 5200 FX 128 MB Card, but it was more worse as clicking open any game would simply shut the computer off while with Radeon it takes 1-2 minutes before the computer shuts down. I have checked the temperatures but they are normal. Power supply is ATX 300 Watts
System Temp 26C/98F
CPU Temp 37C
Northbridge Fan Speed 0 RPM
CPU Fan Speed 2596 RPM
CPU VCore 1.42V
12V 11.73V
3.3V 2.99V
5V 5.13V
5V SB 4.96V

Is it the motherboard or the processor.

p.s I have been using these games perfectly when I was using a Celeron 1.7GHZ on my ASUS P4533MX motherboard with ATI Radeon 7000 64 MB card and such problems never occured.