CPU running but no display

[win32.tr0jan]

my friend is having corei3 3.2Ghz,6GB DDR3 Ram,iBall sprinter 600W and Intel DH55TC motherboard.The problem is that his PC gets off automatically after sometime.He used thermal paste and now for 3 days it was running smooth.Today when he was using photoshop,it got off...and now it aint turning on.what could be the problem??
its urgent..

[Cybertonic]

The problem lies with the power supply according to me. These cheap power supplies rated high amounts of wattage hardly deliver 200-300W of unclean power. He should buy at least FSP saga II 350W 1.4k. Also first ask him the brand of the RAM.