Unable to boot PC

I tried to restore but couldn't because I needed to enable system protection in C:
Eventually I put this in the command prompt

c:
Cd\windows\system32\config\regback

I received "The system cannot find the path specified"
I can get into c:, but no part of the next command has worked.

Ask for any information you think will help and I'll try to give it to you the best I can.

And no, I have no idea why something like that would get deleted, I sure as he'll didn't do it. I had no viruses as far as I knew, I shut down my computer normally, and when I booted it up, it was just gone.