640x480 - 785
800x600 - 788
1024x768 - 791 16 bit
1024x768 - 792 24 bit
1152x864 - 355
1280x1024 - 794
1600x1200 - 798

There is a different method for adjusting screen resolution at boot time. Use the vga=794 cheat code for example for 1280x1024 screen resolution. It may work better for you.

Above are some typical ones you could try.

Note, you have not said what kind of video card you are using. If it is something really old, say with only 4 mb of memory on the card, you may well be stuck with 800x600.

Hope this helps.

sakiZ