hi im running an amd 4800x2, 1024 2x512 corsair ram, xfx 7800gt, and an asus a8n32 mobo, the problem is when i simply run normal apps it is fine when i surf the web its fine but when i play games, it runs for about 10 mins and then the computer shuts down, i can restart it right away but if i try yo play again the same thing happens, i think it is the psu its a 400watts psu or what else could it be??? thx in advance any help is much appreciated, btw how could i know if i need more power