Reset Video Modes

I just got Mepis installed, but I changed the video modes (vertical and horizontal frequencies to be exact) and now it won't start up.?? Is there a command line option I can add to reset the video modes?

Also, is it possible to change the video card? I have a Trident PCI card which is pretty old driving a little 9" in win XP, but now when I start Mepis it shows on the little 9".?? The other is on a geforce 2 AGP card.?? The Trident PCI is set as the default in the BIOS because it won't run with both cards if I set the AGP one as the default.

Thanks for the help in advance.