I have been having difficulty running Windows 7 from the physical disk in VirtualBox on Ubuntu 14.04 LTS.
Installed VirtualBox using the Software Center, and created a Windows 7 VM and empty virtual disk, as a test.
Tried to start the VM and VirtualBox complained about a driver version mismatch. Since the version of VirtualBox was not the latest, I downloaded the latest (from here) and installed it.
After a few attempts to start VirtualBox and the VM, VirtualBox was complaining that another version was running. Thinking I'd start anew, I restarted the host Ubuntu machine.
So, the question is, how to run Windows 7 from a real disk in VirtualBox?