Dropping randomly too desktop while playing games.

I've lately had this weird issue while im playing games, it just drops to desktop every 5 minutes, and if i press any letters on my keyboard it makes a sound as if a program denies it (don't really know how too explain it better, hopefully you understand). There is no error or such, i can just click again on the game icon, but it will dropp out after 5 minutes.
This happens also while i surf the internett and do other stuff. The drops dont always occure, but when they do, they occure every 5 minutes, almost precisely, as if it was scheduled or something.

Ive tried reinstalling graphic card, sound drivers, and installing older versions with no luck. I've tried closing almost all active programs (including desktop manager and sidebar), without any luck.
It seems as i have some kind of invisible program

System Specs:
Intel i5 750
Gainward 295GTX
4GB ram
Creative X-fi Gamer soundcard

Yes, there is no registered event when the incident occures...

Does your mobo have onboard video? If so, remove your video card and use the onboard to see if it persists.