Serial ports COM3-COM49 used, but not listed in device manager

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?

Solution 1:

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

devmgr_show_nonpresent_devices

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.