My PC is restarting suddenly.

My PC is restarting suddenly… i dunno wats the problem… i reinstalled the OS too… i scanned for virus too…. i didn’t got any solutions for that… so, please help me…..
I am using windows xpsp3 oly ..
when i’m opening media player nowadays.. first when i’m playing games like cricket2007 also it will restart..nowadays when i’m starting VLC also it is happaneing like this…..
Answer #1
what os have u got? original or craked?
and can u post ur specs here
thanks
edit:
oh what program do u use bfore it restarts mate?
can u give some more info
thanks
Answer #2
when does it restart? What are you doing when it restarts
Answer #3
Could just happen, it’s still Windows. Do recommend to thoroughly scan you computer for virusses and spyware