Windows 7 When playing a game for a couple of minutes my computer lags a ton

a) have you made sure you can actually run the game? ie: Windows 7/8/Vista/XP/2000/98, 2/4/8/16/32/64 GB RAM, CPU, GPU etc.

b) Random way - can you describe what happens when the computer lags? Or is it actually random (ie: one time it splutters and you smell something burning, next time you see small sparks come out of the chassis etc.)?

c) You say you reinstalled your drivers:
- Which ones?
- Did you get them from the correct place (from the correct site, for the correct product)
- Did you install the driver correctly (so no fiddling around with another program while the driver was installing, for example)

If the game comes from a disc/CD/Flash Drive
Have you tried running the game on another computer, to make sure that it's definitely your computer's problem and not the other.

If the game was downloaded from the internet
Have you:
a) Updated the game to the latest version
b) Looked through the net and see if anyone else has your problems
c) Got it from the legitimate place (ie: not a torrent, from the official site)