Hi there, Just to put a bow on this topic, there are some other recognizes methods as well.
Whenever this has cropped up, I choose this way to handle it and I always reboot when making changes at a system or OS level.
To remove unused COM ports from Windows 10, you can:
- Right-click on the COM port
- Select Uninstall
- Do not check the box that says “delete the driver software for this device”
You can also remove COM ports by:
- Clicking Start
- Selecting Run
- Typing regedit and clicking OK
- Navigating to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter
- Selecting all in the Data section
- Selecting Reset to zero (0)
- Closing the registry editor
- Restarting your computer
You can also use the Command Prompt to check the COM port:
- Type devmgmt.msc to open the Device Manager
- Select View > Show hidden devices
- Open the Ports (COM & LPT) section
You can also use COM Name Arbiter to remove most of the risk associated with modifying the Registry.
I use this method myself,
"Device Manager window open. Click “View” in the menu and select “Show hidden devices”. Expand “Ports” to list all COM ports used. Right click on one of the greyed out ports and select “Uninstall” .
thats it. Reboot.
HTH
YMMV
GL 
PJ 