I connect to my Win 7 computer using an Android remote desktop client. I close the session, and then sit down in front of the Win 7 computer. After doing this, the Win 7 computer is very sluggish. Nothing helps except rebooting. Any idea why this is happening and how to fix it?

While its sluggish, open the task manager in Windows 7 computer and see if you can identify which process is taking up unexpected CPU and/or memory.

No process in particular stands out from the crowd as a big hog.

Did this start recently? If so, I would suggest you perform a system restore to a point in time where the system was stable. Maybe you updated a video driver or something recently?

It started when I successfully got remote desktop running for the first time, which was last week.