Until yesterday I used a Windows 7 Pro and OpenVPN to connect to a VPN. In the OpenVPN config folder I had:

  • ca.crt
  • client.key
  • connection.ovpn

Due to some hardware failure I was forced to buy a new system that came Windows 10 Home pre-installed.

In Windows 10, I'm trying to use the built-in VPN connection system, in order to avoid installing OpenVPN, but I'm unable to make it work. I installed the ca.crt in the MMC, in Trusted Root Certification Authority, but when I press Connect it says "Can't connect to VPNCONNECTION - A certificate could not be found that can be used with this Extensible Authentication Protocol". I tried various settings, but no luck (and for me it's really a matter of luck, since I don't know what I'm doing there)

I installed OpenVPN, copy-pasted the config directory contents from my old machine and it connected just fine.

Is there any chance I can use the Windows 10 built-in system and uninstall OpenVPN?


  • The error message suggests that either, client device or client user certificate is missing on Windows box. CA cert is required to establish a trust, however there should be another certificate (with private key) to use for client authentication.
    – Crypt32
    Jan 17, 2017 at 16:57
  • I do have the client.key file which contains a private key. Is this what you where referring to? If so, how should I use it? Thanks!
    – VMC
    Jan 18, 2017 at 11:53
  • yes. You have to merge client.cer (it may have .pem extension) and client.key files to single client.pfx and then install it to Windows Certificate Store. (Current User\Personal)
    – Crypt32
    Jan 18, 2017 at 12:48
  • Well, unfortunately I have no client.cer, nor client.pem, so I'm a bit stuck on this. But thank you for your time.
    – VMC
    Jan 19, 2017 at 10:40

1 Answer 1


You can't use the built-in VPN for connecting to OpenVPN. The Windows VPN client only supports the protocols L2TP, PPTP, IKEv2 and Microsoft's SSTP. OpenVPN is a SSL VPN, and the thing with a SSL VPN is that every company has its own Secret Sauce for the connection parameters. While in the future Windows could look into adding support for OpenVPN in particular, in that case the Protocol field will clearly call out OpenVPN.

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