there are a 5 modes for dual monitors, my possibilities:
dualview (my current) desktop as normal on one, and other just has background (no start bar) and u can just drag windows onto it! i commonly use it for watching video on one screen! or having msn up on one, and IE on other. all you do is pull windows straight across, very nice, simple
horizontal span: the regular desktop is stretched horizontally over both monitors! good if you have two exact same monitors with a small bezel around side! so ya can push em together and get almost perfect widescreen! seen fantastic gaming with it (halo i know for sure works great like this)
vertical span: as above but spanned vertically! would be a more difficult setup, never used it but hey i guess some will.
clone: normal desktop behaves exactly like having one monitor, second one is exactly what you see on first!
single display: not really a dual monitor option! but its listed! i doubt this needs explaining lol but.. basically you pick a monitor to use, and it turns off the other one! pretty simple!!!
simple explanations of the modes available for dual monitors on an asus fx 5700. hope this helps
personal note: dual monitors great! i dont know what id do without it! top two modes iv listed obviously best! i love dualview!