Oracle VM crashes - how to fix

Runtime error opening 'C:\Users\You\VirtualBox VMs\Linux Foo\Linux Foo.vbox' for reading: -102 (File not found.).

If you're using Oracle's VirtualBox, this might happen to you sometimes, such as when you shut down your computer with programs still running, and the shutdown process hangs. Although it look daunting, it could be an easy fix:

1. Shut down VirtualBox completely.
   
2. Open your VM folder (use the path mentioned in the error message)
   
3. You are supposed to have a .vbox file there, but you will probably have a .vbox-tmp or .vbox-new file instead, or at least a .vbox-prev file.
   
4. If you see one of these, and you DON'T see a .vbox file, then rename the tmp/new/prev file to have a .vbox extension
   
5. Restart VirtualBox