Computer crashing when playing any game

After i finished with the BSODs a new problem happened my computer was keeping crashing in everygame i was playing.When i was playing for like 2 hrs or even 10 mins a lag apears then my comp reboots with a black screen appearing.I took my computer to a repair service.It turned out to be something with the motherboard(not the motherboard itself).So i renew a piece from my motherboard.Then yesterday i was playing bioshock then i heard a sound like a Ptsssswuuu from my comp then for 2 mins everythng in my comp freezez i tried playing other games like skyrim nad mount and blade.At skyrim is the same but at mount and blade its something else it freezez for 1 minute after starting to play and then it works perfectly well perfectly after it loads everything because at the start everyman is bald.So i think that my computer new piece wont let my coputer rebot because I was hearing that sound with 2 secs before my comp resterted and now it freezez and my dad tell me its a softwere problem and i should reinstall my windows or geting mac because therer are not so many problems with mac.But i want a pro opinion so whats your opinion i should do?


comp specs: Windows 7 x64
GFX card:ATI REDEON HD 5670
Processor: Intel(R) Core(TM) 2 Duo CPU E 7500 @2.93 GHz
Audio:Relatek High Definition Audo
Ram: 4 GB
Motherboard:? i dont know


before asking me about any dmp.file my brother deleted acidently them and i didnt recive any BSODs for a month its true i havent done anything to it after the BSOD but everything seemed to e fine until this.

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