I have a Toshiba Satellite laptop with a Mobility Radeon x200 IGP and a dual boot system of Ubuntu 8.04 and Windows XP MCE. I have it attached to a CRT that's capable of 1600x1200 at 75 Hz, and in XP I can use the two screens fine. In Ubuntu it will only run at 1280x800 at 60Hz (the same as the LCD on the laptop), and only as a cloned screen, not an additional display.
I've found sites telling me to edit my sys.conf file (or something along those lines) but that pretty much shoots straight over my head in terms of the information required. Does anyone have any advice?