Some piece of software or some driver appears to be using the serial ports COM3-COM49.

New COM ports for Bluetooth et al get assigned ridiculous numbers over 50. When I try to change the number, Windows claim that the lower COM port number is in use, and suggest that I don't apply new settings. However, ActiveSync docs say that COM port number must be 20 or lower.

I have no idea where to look to figure out what's reserving the all those COM port numbers. What other ways do I have for uninstalling devices that don't appear in device manager? How do I figure out what took over those COM port IDs?

1 Answer 1


Go to My Computer, Properties, Advanced, Environment Variables, and make a System variable named


Make its value 1.

Now go to device manager, view, and check Show Hidden Devices.

Now expand Ports(COM & LPT). You'll see more ports than you did before. Right-click on and Uninstall whichever of the greyed-out ports you don't want.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.