I was watching a movie and playing a video game (both half-screen), and the game froze up and I couldn't get task manager to start. I waited a bit to see if things would resolve, and after they did not I restarted (manually) only to get insert proper boot media type message. I restarted again and was unable to get into safe-mode (same insert proper boot media type message). Entering the BIOS the main boot device had been changed to my storage drive (not-bootable). I was able to change back to my OS drive and boot into Windows, but I'm kind of concerned. Is there any way I can look into what might have happened? As far as virsuses, I use AV and browse sandboxed, perform boot-time scans, and am generally pretty cautious.