This enables multiple concurrent users on Windows 7:
- enable remote desktop login in the control panel
- install the UniversalTermsrvPatch
- create multiple user accounts
- each user can access the machine via remote desktop concurrently
Full explanation at http://www.zahirkhan.com/
Update: to make it work under Windows 11, check out http://woshub.com/how-to-allow-multiple-rdp-sessions-in-windows-10/