How to specify to MSTSC which session to connect to?

Solution 1:

Use Local Security Policy (or Group Policy if the machine is in a domain) to limit users to a single RDP session.

Open Local/Group Policy.

2. In Computer Configuration, Administrative Templates, Windows Components, Terminal Services, double-click the Restrict Terminal Services users to a single remote session setting.

3. Click Enabled, and then click OK.

Note: Replace "Terminal Services" with "Remote Desktop Services" if on a modern version of Windows.

Solution 2:

I found another great answer to this question here: http://sqlservertimes2.com/?p=55.

If you connect to a remote desktop and it creates a new session instead of connecting to your existing session, do the following:

Run taskmgr and go to the Users tab and note the ID number of your previous session.

Run tscon n where n is the ID number. Your remote desktop session will be immediately switched to the specified session.