You may have multiple instances of unknown devices in network section of Device Manager.
If you take a look at their properties, you will that everyone of them is VirtualBox Bridged Networking Driver Miniport. These are leftovers of previous versions of VirtualBox present because of the issues regarding permissions in registry.
I had an amazing number of 41 such unknown devices.
Because they refuse to uninstall the normal way, they have to be removed manually.
You will need to have administrator rights to take ownership and give yourself full permisions and auditing control for the following registry key in order to delete it, as this registry key is all that is left of them:
When you got rid of it, reinstall VirtualBox to make sure everything works fine.