Windows 10, VPN and slow DNS lookups

Disable IPv6 both on your NIC and the VPN. That did it for me.

If in the current version of Windows 10, VPN seems to have too many problems, this might leave only two options :

  1. Wait for VPN to be fixed in Windows 10
  2. Downgrade to Windows 7, as described below :

If you have installed Windows 10 over Windows 7, and you have kept the resulting folder C:\Windows.old, then you can use it to return to Windows 7.

This is the procedure :

  • In the Windows 10 Start menu select Settings
  • Click Update & Security
  • Under "Go back to a previous version of Windows", click Get started
  • Enter some angry message text into the "Why are you going back?" screen
  • Click Next and wait, as this will take some time
  • You will need to have your password to Windows 7 once the process is finished.

This is further explained in detail with screenshots in the article : How to downgrade Windows 10.

If you have deleted the Windows.old folder, a clean install of Windows 7 is probably the only remaining way to downgrade.

Ensure that you have a complete backup of your data before starting.

(Note: Remember that this answer is from 2015.)