I know it's probably too late and probably nobody cares, and probably nobody use so old windows version like win 7 or simular, but let it be there.
If you stuck with such problem and nothing helps, but you don't wana reinstall your system to fix the problem, just go to C:\Program Files\OpenVPN\bin
tapctl.exe list
tapctl.exe delete <your tap adapter name>
tapctl.exe create
tapctl.exe create
Basicly this is simple workaround, so you have 2 tap-adapters, one is enabled by default when windows is loaded, but second is disabled and openVPN can use it so error will dissapear. Workaround tested with OpenVPN-2.5.6-I601-amd64.
Second problem which was never fixed propertly, but mentioned many times, ghost adapter which doesn't exist and can't be find even with
device manager -> show hidded devices. What if you got error during installation of OpenVPN and as the result next time you will try to install it y will get such crap like:
TAP-Windows Adapter V9 #2, TAP-Windows Adapter V9 #3, TAP-Windows Adapter V9 #4 after install in device manager.
How to fix with regedit:
Delete your adapter with
tapctl.exe list
tapctl.exe delete <your tap adapter name>
or using uninstaller.
Find descriptions folder with proper ClassGUID:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4D36E972-E325-11CE-BFC1-08002BE10318}\Descriptions]
Here you will see something like: "TAP-Windows Adapter V9"=1,2,3
Just remove all this ghost adapters from this line. That's all.
