Has it ever happened to you that you tried to change a device’s port to a specific COM port only to find that it was in use, yet there was no device present in the device manager? This is because the device that is using that specific COM port is not really present in your system but the device driver for that device has claimed that COM port for its use. You can easily view which of the devices have been configured to use which of the COM ports in Windows by viewing the hidden devices.
- Press Win+R to open the Run dialog.
- Type devmgmt.msc in the Run dialog and press Enter to open the Device Manager.
- In the Device Manager window, select View → Show hidden devices from the menubar.
- Now you will be able to see all the devices including the ones that are hidden because they are no longer present in your system.
Above instructions work for Windows 8.1 and 10 without any problem. But if you are using Windows 7 (and earlier versions), then you will have to do some extra work before using the above instructions.
You will have to set an environment variable DEVMGR_SHOW_NONPRESENT_DEVICES and set its value to 1 in the following manner:
- Press Win+Pause to open the System information window.
- Click on Advanced System Settings from the left side in this window that is displayed.
- Click on the Environment Variables button in the System Properties window.
- Under the System Variables section, click on the New button.
- Type in the variable name as DEVMGR_SHOW_NONPRESENT_DEVICES, set its value to 1 and click on the OK button.
- Close all the windows opened by clicking on their respective OK buttons.
Thats it, now you can open Device Manager and follow the instructions as explained in the beginining of this article.