X and Fluxbox :: issue

i have a problem with the x resolution. whenever i boot up it says "passed an undifined mode number" and then some options to manually select one or continue. in dsl the graphics are messed up and can be fixed with changing it using xvesa and 800x480 at 16bit grpahics, but i know my computer can do better. id like to know if this is a monitor issue or a grpahics card issue. i can fix the monitor issue(i have a spare one) but i cant fix it if its a card issue, because it is integrated into the motherboard.

see:

http://damnsmalllinux.org/wiki/index.php/Vga%3Dxxx

original here.