Are you getting an error along the lines of "There are no TAP-Windows adapters on this system"? This is most likely because the installation of the OpenVPN TUN/TAP driver results in registry entries that are incorrect. To resolve this issue you can open the registry editor and navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Class\{4d36e972-e325-11ce-bfc1-08002be10318}

There, go through the entries until you find an entry that has ComponentId and MatchingDeviceID set to TAP0901. Change this to lowercase tap0901. Make sure you go through all entries that have these values set and change them as well. Now you should be able to connect!