Discoloration, mainly green, in Direct3d games

Hi there,
This began happening a while ago, I believe after I updated drivers about a year or so ago.

My problem is the following : I have been experiencing discoloration in just about any game I play on my pc. It wasn't like this when i first bought it. In games, areas of tan and gray colors are streaked with irregularly shaped green lines and/or dots, and I have no idea what to do .. my drivers are all updated and I am dead set on reformatting =[

specs:
bought september 2002
windows xp professional
p4 2.8 ghz
512 MB pc 1066 rdram
leadtek a250 ultra geforce 4 ti 4600
sound blaster sound card (i think audigy, possibly gamer)
120 gb western digital hard drive with i believe 8 mb cache buffer
directx 9.0c

Diablo 2, Counterstrike, and World of Warcraft all exhibit the same problem .. green streaking in gray and tan areas.

Also, when I go to Display->Settings->advanced->geforce 4 ti4600 the "additional properties" button is dimmed out.. this shouldn't be this way and I don't know why it is, although I suspect it is linked to the problem because in the "additional properties" there are configurable Direct3D settings.

Thankyou for your time,
Geesh