To fix an error about a missing kernel driver that keeps telling you to install dkms and run
/sbin/vboxconfig, follow the process below.
Fix error about conflicting Virtualbox versions
This error usually happens when going between major or point releases–say Virtualbox 5.0->5.1 or 4.3->5.1). It can also happen when upgrading Ubuntu say from 14.04 to 16.04.
uninstall your old Virtualbox by
apt remove virtualbox or dpkg -r virtualbox-4.3
reinstall new Virtualbox