In Windows Server 2003, when you use Terminal Services, you can connect to the console session (session 0), and at the same time, open a shadow session to it (as long as you connect from a session other than the console). With this added functionality, you can log on to a Windows Server 2003-based server that is running Terminal Services remotely and interact with session 0 as if you were sitting at the physical console of the computer. This session can also be shadowed so that the remote user and the local user at the physical console can see and interact with the same session.
How to Connect to the Console Session
When you connect to the console session of a Windows Server 2003-based server, no other user has to be already logged on to the console session. Even if no one is logged on to the console, you are logged on just as if you were sitting at the physical console.
To connect from the remote Windows Server 2003-based computer, open a command prompt, and then type the following command:
mstsc -v:servername /F -console
where
mstsc is the Remote Desktop connection executable file,
-v indicates a server to connect to,
/F indicates full screen mode, and
-console is the instruction to connect to the console session.
When you use this command, you open the Remote Desktop session, and when the logon is authenticated, you are connected to the console session that is running on the Windows Server 2003-based server. If a user is currently working on the console session at the computer, you receive the following error message:
The user domain\username is logged locally on to this computer. The user has been idled for number minutes. The desktop is unlocked. If you continue, this user's session will end and any unsaved data will be lost. Do you want to continue?
The user of the current console session is then logged off, and you receive a message that states that the computer is currently locked and only an administrator can unlock it.
Note: If the console session user and the Terminal Services session user are the same, you can connect without any problems.
for more information read article :
http://support.microsoft.com/kb/278845