I tried to find an application that imitates Linux multiple desktops in an at least working manner.
Installed about ten applications, most of them didn't work at all (from my standards).
Many of them also have an ugly impact over Windows resources.
After some hide and seeks on the net I managed to find VirtuaWin, a small app that copies the behavior of multiple desktops in Linux. It has a low fingerprint on system resources and just works, without using killer ways to do it.
Of course it's on sourceforge.net.
You can find it here.
Tested on my Vista don't know about Windows 7.