Virtual Desktop Manager for Windows 7

Dexpot allows you to create multiple, virtual desktops to increase the work area of your screen by up to 20 times. Each virtual desktop is independent from the others and can have its individual wallpaper, resolution, and icons (or no icons at all). You can easily switch between desktops from the tray icon, or via hotkey, or even use an automatic desktop slideshow that rotates all virtual desktops. In addition, you can move and copy windows from one desktop to another among the desktops, set up rules to automatically move, copy or close windows and more. Dexpot is one of the most advanced desktop managers out there, that is easy enough for beginners, but offers some great flexibility for more demanding users as well.

Despite its sophistication, Dexpot is using only 2 MB RAM.

Dexpot is freeware, suitable for Windows 2000/XP/2003/Vista/2008/7 (incl. x64) portable versions are available too.

There are a few third party applications that have all the advanced graphic rich features of other operating systems, but if you just want a working, light-weight solution, I recommend Microsoft / Sysinternals Desktops

The popular VirtuaWin is a free and open source virtual desktop manager for Windows. It advertises support for Windows 9x/ME/NT/2000/XP/Server 2003/Vista, although I assume that part of the site hasn't been updated as it works fine on Windows 7.