Run xf86config (might be different for RH 7.1--someone who uses RH please correct me here). When it asks if you want to enable virtual screens (screen size larger than actual screen size) select No. Additionally, try pressing CTRL+ALT++or- (use the +/- on the number pad on the keyboard, not the ones next to the zero and backspace key). This will toggle between the resolutions your monitor and video card can support. If it gets to the right screen resolution you're set. Additionally, you can open up a terminal in Gnome or KDE and do the following:
password: <enter root password>
You should see a file called XF86Config. Open it up using your favorite text editor and then go down to the section regarding your default resolution rate. You can edit it to what ever you want (32, 24, 16, 8, etc.) Below that, you'll see what resolutions you have set for each of the rates. If you want to set it so the default is 16 bit with resolution of 1024x768, then change the order of the resolution rates where 1024x768 is first in the list:
"1024x768 800x600 640x480"
This will make it so that everytime you "startx" you'll get the default of 1024x768 at 16bit color resolution. I would recommend first running the xf86config program (remember it could be called something else like xconfigure or xconfigurator or something like that). Hope this helps.