Clear old comm ports

How do I clear the old comm ports that are not being used anymore?
Every time I install my USB to RS232 adapter it adds another one, I think I am up to 20 or so, but the program I use only goes up to 5 so I have to keep changing it when I use that program.
I am running windows 7 32 bit professional.

Secondly is there anyway of actually knowing if there is something actually attached to a particular comm port? It says it is in use but I know all of them are not being used, some though maybe, so how can I be sure?

If you go to Control Panel \ Device Manager
Expand Ports (COM & LPT)
Right-click and Uninstall

This would be my guess as I have never heard of your specific situation.