no os files

My grandson's computer wouldn't start yesterday. Supposedly the last shutdown was just a normal one, but we ended up with a dark screen with a prompt on start up. I used the function key (I think f9, but could have been f11, lol) and ran a test to diagnose the problem. The result said that there were no os files. I backed up his files onto an external drive and then used the restore disks. What could have caused this problem? I was unable to access the installed repair or anything. Was there anything I could have tried besides what I did?

It sounds like you did the right things. You might want to monitor the hard drive for issues every so often.

One thing I did think of, on my nephews machine I make sure all the system files are hidden so he doesn't accidentally delete them. In Windows Explorer, select Organize, then Folder and search options, click the View tab, and select Don't show hidden files, folders, or drives and also check Hide protected operating system files (Recommended).