Please guys......i really need the help

heyas, i got a p3 450 128 ram and i got a tnt 2 m64 with 32 meg…when i play games in open gl counterstrike, and quake3 the screen flickers in q3, and in counter strike u try connect to a multiplaying game and u get no luck cos ure screen gets coverd with flickers and u need to reboot becuase it locks i am running windows 98 and i have a gigabyte motherboard thanks ppl