Query and Reset a Terminal Server Remote Session

If you want to know which users are connect to a specific Server you can use the command :

qwinsta /server:IP_SERVER

If you want to disconnect a specific user you can use the command :

rwinsta /server:IP_SERVER SESSION_ID

http://weblogs.asp.net/owscott/archive/2003/12/30/Managing-Terminal-Services-Sessions-Remotely.aspx