There is no official / approved way to do this.
Multi-user Remote Desktop (aka Terminal Services) is only supported on Server versions of Windows, and then only with the appropriate client access licensing.
There is, however, a 'hack' that will allow other users to log into a Windows 7 PC using remote desktop. I won't post the steps here, but there's a working version at the following site:
http://experts.windows.com/frms/windows_entertainment_and_connected_home/f/114/t/79427.aspx
Note: This is unsupported, may be broken by future updates, and is almost certainly in breach of your Microsoft license agreement, but it does work, and I happily use it at home on a Windows 7 Media Centre PC so that I am able to perform background changes without logging off/blocking the main MC user.