HELP! Can't see bottom 1/4 of screen on certain games

I have an ATI radeon 32mb pentium866 win98 2nd edition Many first person games such as RogueSpear CS GhostREcon Enemy Engaged the bottom 1/4 of the screen is not viewable. I have downloaded the latest drivers and patches and even changed some opengl settings nothing has worked it’s probably something stupid but I’m at my wits end please HELP!