There’s a great GUI out for OpenVPN & Windows, located here.
However, this GUI includes an old OpenVPN, that is no longer compatible with Windows 7 and Windows Vista.
The TUN/TAP driver will be blocked due to compatibility issues, and when trying to connect to a VPN, you’ll get an error along the lines of:
All TAP-Win32 adapters on this system are currently in use
The simplest fix, is to install the GUI package (including the old OpenVPN binaries), and reinstall OpenVPN afterwards.
This will overwrite the old files and update the driver with a Windows 7 compatible driver.
Try to connect now, everything should work like a charm. 🙂