Colour problem

[Cave]

Alright, so I got my new PC, but have a small (but somewhat annoying) problem.

The game runs fine and all, but the graphics appear blotchy? The colour is screwed up.

Screenshot

Screenshot 2

Screenshot 3

This isn't limited to San Andreas either, it's like this with everything.

I googled the hell out of it, but found nothing. I also spent a long time messing around with the monitor settings, to no avail.

GTX 260.