Okay, then the hardware should be okay.
Since then I reinstalled windows 7 so I can't see what could cause this. Fresh reinstall, 10 days or so.
What software had been installed? Some games and even some music CDs install rouge copy protection drivers. No idea if such is prevented by Windows 7.
What you could also try: Run a Linux Live system, like Ubuntu or Mint. They also allow creation of a bootable USB thingy. This is an excellent method to find out if an issue is due to some Windows oddity or not.