(This is a Windows problem only).If you get that error it seems like your VirtualBox installation missed installing the vboxdrv.inf driver. Please first try to reinstall VirtualBox - if this does not solve the problem, go to C:\Program Files\Oracle\VirtualBox\Drivers\ and double click in the file vboxdrv.inf. After that, you should be able to run VirtualBox without problems.
VirtualBox shows me the following runtime error message: "cannot access the kernel driver!" What can I do?