failed to start Virtual Device in Oracle Virtual Box

Solution 1:

I had exactly the same problem as you, tried everything, but the solution is really easy:

1. Open network center
2. Change adapter settings
3. Right click your Virtualbox host-only adapter and select Properties
4. Enable "Virtualbox NDIS6 Bridget Networking Driver" (if it's disabled - if it's not, see next)

If the checkbox in step 4 was disabled, VB should work just fine now (no reboot needed). Otherwise repeat steps 3-4 for every network adapter you have (Ethernet, WiFi...) and always uncheck the NDIS6 checkbox -> apply -> check it again -> apply.

Hope this helps - worked for me on 2 different machines (it seems that this is caused by last Windows 10 update - thanks Microsoft for wasting another 4 hours of my life).