TAP-Win32 Adapter Is Not Coming Up: "Initialization Sequence Completed with Errors"
In Control Panel / Administrative Tools / Services, make sure that the DHCP Client Service is started.
If the above fix doesn't work, then it's possible that the TAP-Win32 adapter is being firewalled. In general, it's safe to disable the firewall on the TAP-Win32 adapter because OpenVPN ensures that only an authenticated machine on the other end of the connection can communicate through it. However, there have been reports that certain third-party firewalls will block the TAP-Win32 adapter after an XP SP2 upgrade.
You can also try changing the ip-win32 setting to a non-DHCP method. For example:
ip-win32 netship-win32 ipapiip-win32 manual
For more information on managing tap-windows drivers, look here.