The other day, I was setting up a win7 machine to grudgingly get ie9 up and running (for 10k submission). In any case, set up a new VM with Virtual Box, use a win7.vdi, and tried booting it up. Kept getting the blue screen of death (i know! funny - it’s still in use) which would flash away before I could even read what the error was. Windows repair didn’t do much. The same .vdi was working fine for a colleague.
So, to help anyone else with this issue, try checking your Settings > Storage on the VM. Could just be a hardware mismatch.
Before fixing it
Turns out the new machine was created with the primary drive being a SATA. Switching it over to IDE fixed the problem right up. Here’s a pic of the settings panel - set up correctly, at least in my case.
After fixing it
If this doesn’t help your problem, well, best of luck.