Over the weekend I (finally) figured out how to set up dual monitors on my Radion 9200 Dual head Vid Card... it was actually very easy once I followed the right instructions. Basically all you have to do is modify /etc/X11/xorg.conf file and add a few lines to the video card device section. That';s it ... Before that I tried a half dozen other methods ... including installing open source and private drivers... for this you don't have to do a thing except edit one file.. here is the link

http://www.ubuntuforums.org/showthread.php?p=1773710

This should work for basically any ATI card, if you have nVidia sorry but there are a few methods to try on this link as well

http://www.ubuntuforums.org/showthread.php?t=221174