How to clean up com ports in use by the system which are actually not in use.
- Run REGEDIT to edit the Windows Registry.
- Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter
- Now on the right panel, you can see the key ComDB. Right-click it and click modify
- In value Data section select all and delete reset to Zero (0)
- Its 32 bytes with 8 bits in each byte. A set bit makes a port number (1...256) reserved. enter image description here
- Close Registry editor and then restart your computer. All COM ports are now Free.
- You may need to reinstall any USB-to-serial converter.