New built computer crashes/freezes help

[kenq86]

i recently built an i5-2500k w/c i havent overclocked yet the thing is whenever i play games w/ it like bullet storm star craft etc it freezes/crashes after 10-20 mins..im using a radeon 6850 and a 775 thermaltake watts bronze psu..ran a test on my ram and its all good,updated all the drivers, ran furmark stability for an hr-good as well..all temperature are stable..so what could it be?..bad gpu?..or psu ? or should i increase the voltage on something? pls help..pretty much it just crashes when i play games

 

[JackNaylorPE]

What were CPU / GPU temps at time of crash ?

What was BSOD error message ?

Was the memory test you ran Memtest86+ ?
http://www.memtest.org/

Was memtest an over night run w/ no failures ?

Did it pass overnight run of Prime95 ?

What does Event Viewer say ?