VirtuaWin - VirtuaWin is a virtual desktop manager for the Windows operating system (Win9x/ME/NT/Win2K/XP/Win2003/Vista/Win7/Win10). A virtual desktop manager lets you organize applications over several virtual desktops (also called 'workspaces').
WindowBlinds - WindowBlinds is a computer program that allows users to skin the Windows graphical user interface.
Sysinternals Desktops - Desktops allows you to organize your applications on up to four virtual desktops.
bbLean - Alternative Windows shell
9Desks - up to nine virtual desktops
Cairo Shell - Cairo is a desktop environment for Windows.