immediately after the pc restarts turn it back on and goto the BIOS by pressing del..(maybe diff depending on ur mobo)...thre check ur processor temperature....it should be in a subsection called hardware monitoring....if its anywhere above 75 C then its a heating prob and u need to check ur airflow and cab fans....if its normal then check ur gfx card temp after turning on the pc and right click on desktop>settings>advanced>geforce 7600 gt>temp setting......it should not be more than 75 (atleast my friends dosent go beyond 75

)...iff the prob is not here also then its most probably a failing PSU( do post the wattage)...