About every 5 minutes I play any newer game, my computer lags for about 2-3 minutes, and then runs smoothly again. The lag reduces framerate to less than 1/sec. It's all very weird, for instance, it happens in Fallout: New Vegas, and Civilizations 5, but not Heroes of Might and Magic 3.
The computer does not make any unusual sounds during this, except the fan spins a bit louder, as I guess it's working hard to keep up what ever trickery it's trying to do.
It started when I reformatted my computer, and upgraded from Vista to Windows 7 (through deleting vista, and installing windows 7, not by upgrading), before that, there were no problems.
Motherboard: abit Fatal1ty FP-IN9 SLI
Graphic card: NVIDIA GeForce 9600 GT
Processor: Intel Core 2 Duo
Memory: 8GB RAM
Here is a list of things I've currently tried with no result:
Changing settings in the games from high to low to high
Deleting the graphic card driver, and reinstalling it.
Changing settings in the NVIDIA controller, such as, disabling anti-alias, setting all settings to low, or disabling what ever was possible.
Tried various patches for the games themselves.