video card

I bought a new 17 inch monitor for an older (1999) IBM computer that came with a 15 inch monitor. I can?t get a 1024 X 768 resolution
higher than 16 bit color. At first I assumed the video card wasnt capable of it but then realized 800 X 600 fillsthe screen on 32 bit
color.
At 800 X 600 or 1024 X 768 the video card is powering the same amount of real estate. Things just look larger or smaller on the
screen.
When I try to set it for 24 or 32 bit color the resolution setting automatically readjusts itself to 800 X 600.
I downloaded and installed new drivers. Ive tried everything I know how to do. Does anyone have any ideas?
Windows 98. Video Card : ATI RAGE PRO TURBO AGP 1X.