Hi there
Do you mean something like Linux has where you can effectively have a number of Virtual Desktops all with their own wall paper / menu's apps etc. Most also will copy apps over from one to the other too.
Or do you mean to have a single desktop much larger than the physical size of your screen where you can just move to the part of the screen you want to see.
XP had the former. Windows 7 As far as I know doesn't have 100% decent softwre for this but you could try this which is probably the nearest you can get to what I think you want. It's not too bad.
Free Dexpot Download
heers
jimbo