Here is a tip to be able to solve this type of problem for future users:
copy the following two lines into notepad:
set devmgr_show_nonpresent_devices=1
\windows\system32\devmgmt.msc
Then save this into a batch file, e.g. "Show Old Devices.bat"
Then start the batch file (double-click in Windows). It will then load your Device Manager.
Now when you click on the menu "view", then "show hidden devices", you can see all your
old devices you no longer use under the COM ports. Then you can delete these or change
their ports to prevent a conflict.
Note that I only have German Windows on my computers, so I think these are the English
menu titles.
73,
Mitch DJ0QN / K7DX