Windows server RDP session remote control

I have RDP access and administrative privileges on Windows Server 2008 R2. While other users are connected via RDP, I can remotely contol their session. When user is disconnected (but the session is still alive), I can't use remote contol for some reason. Is there any way to login to user's se开发者_开发问答ssion without entering his password?

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http://support.microsoft.com/kb/281156

Cannot remote control a session which is in disconnected state.