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I need to install OpenVPN (using the latest stable, OpenVPN 2.2.1) on a Windows 2008 Server R2. All works fine, except I can't seem to install the TAP adapter. Running addtap.bat (as administrator even with explicit "run as administrator") or re-installing OpenVPN does not produce any errors, but running OpenVPN fails: "CreateFile failed on TAP device" and "All TAP-Win32 adapters on this system are currently in use."

Looking into Window's hardware manager shows the TAP adapter with a warning symbol, status: "The driver hasn't been installed because it produces errors with Windows; you must restart your computer." (freely translated from German) Now, after rebooting, the TAP adapter is GONE completely!

Need urgent help, any input appreciated! Thanks!

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up vote 0 down vote accepted

Seems the problem caused by "drivers signing (integrity check)" feature.

You can disable it temporary (one time till next boot) by pressing F8 while reboot and selecting "disable digital signature enforcement" option.

To disable this feature permanently you can use the command:

bcdedit /set loadoptions DDISABLE_INTEGRITY_CHECK

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