If you are having trouble with your COM ports stacking up because they are in use, these brief steps below will help you clear them out. (I found myself the other day needing to connect via a USB to Serial adapter to a server and noticed that 35 COM ports showed in use. Somehow the COM ports were not getting cleared out.)
One thing is to see if hidden devices are taking up the ports:
Click Start > All Programs > Accessories and then click Command Prompt.
Type set devmgr_show_nonpresent_devices=1 in the Command Prompt and then press Enter.
(you might have to restart your computer after this)
Type cd \Windows\system32 in the Command Prompt and then press Enter.
Type start devmgmt.msc in the Command Prompt and then press Enter.
Click View > Show hidden devices. This will display devices that are not connected to your computer.
Now if you expand the section on COM ports, all the COM ports that have ever
been created will be displayed, the non present ones being in grey. You can
uninstall away anything that you don’t want (right click, select uninstall).