My (12-year-old) son's computer won't boot. It's a Dell Inspiron 17" running Windows 8, bought in July 2013. When I turn it on, Dell logo comes on and then in upper left it says "Checking Media [fail]", then "checking media" again, then "No Boot Device Found. Press any key to beboot the machine". I insert a USB recovery drive (it was made for my Toshiba that runs Windows 8.1, but it should work anyway, right?). I choose US keyboard layout and it then opens into Recovery Environment. I choose Troubleshoot → Refresh Your PC. Message appears "The drive where Windows is installed is locked. Unlock the drive and try again." I go to Troubleshoot → Startup Repair, which runs and then says "Startup Repair couldn't repair your PC." I then go back to Troubleshoot → Command Prompt and run chkdsk on Windows drive (c:). It says "Windows has checked the file system and found no problems." Dell would probably tell me it's a hard drive failure and tell me to buy another one. But my son has a lot of things on this computer he'd like to keep, and I have a funny feeling that all his stuff is still there if I can only figure out how to fix this boot issue. I will make him put a backup procedure in place once it's running again. I just need to get it going.
All help will be greatly appeciated.