Reboot your computer. When the first image shows up (on my M10000 it says 'EPIA MAINBOARD' or something like that) hit the Del key on your keyboard. This will bring up the CMOS settings screen, a text menu that lets you configure your motherboard. You should find the 'Monitor type' somewhere in one of the menus, maybe the 'Chipset Configuration' menu, I can't remember (and my car is down in my garage and I'm stuck on a conference call right now).

Hope that helps, I'll be checking here frequently.