If you have an ATI video card, then they have a program that does multiple desktops, I think it's called Hydrovision or something. It's free to download together with the ATI drivers
Sysinternals indeed does contain a program for that as well, but I never managed to get it work right and I read somewhere that there are known issues with it.
I have not researched the multiple desktops issue with any diligence, since I have not found a good use for it, I prefer to have multiple monitors instead of virtual desktops, but this is what comes to mind.
My 2 cents.