virtualbox.org

I'm running VirtualBox 5.0.12 on Windows 7 with a single Linux 64-bit VM (setup by boot2docker). The VM was running just fine, but after a failed attempt to install the Guest Additions Image, the VM no longer launches. I've powered off and restarted several times, but the command prompt starts and just hangs on a blank screen.

Could it have something to do with the storage settings? I've was playing around with those to get the the Guest Additions Image installed.

1) boot2docker is not supported here. Try plain VirtualBox, in which case the following questions would apply.
2) How did you try to install the GAs? See the user manual Ch. 4.
3) You were "playing" with the storage settings to install the GAs? Why?
4) You don't mention your guest. See Minimum information needed for assistance.

But remember, questions 2-4 apply if you run VirtualBox. Not boot2docker. So, start from #1...