Geforce 4 Overheating i think??

Hey guys....i have recently bought a Nvidia Geforce 4 ST Lab vid card. But now when i play games the graphics tend to play up as in wierd shapes, different colour, like slashes across the screen at times. This could happen in 10 minutes or a hour, then it may affect my desktop also with some red dotted lines across the screen or something irregular. I have a AMD 1.3Ghz, 256 DDR RAM, Gigabyte GA-7DX(R) M/Board. I have the lastets detanator drivers and directX 9 so i doubt it is software.........????? Also i have my NIC card in the below slot of the video just for the record?? Could this be the problem?? NOt enough air or something, that is if it is overheating??

P.S There is a picture attached to show what i mean in the desktop........thanks guys and gals