OS Drive Incompatible/Disabled

Hello!

I usually don't have problems with my PC but I am currently unable to use it as a result of something happening with my main hard drive (software related) and I would really appreciate any help or knowledge on the issue. I've looked everywhere for a solution but it seems to be kind of out there...

There was a recent windows update that installed (last week); I noticed my PC freezing up a bit for a few moments, I looked on task manager and saw 'windows update' using a lot of my resources. Windows updates don't usually cause my entire system to lag out... it was strange, however I didn't think much of it so, I let it install, restarted, and went upon my day. 

The next day I went out for a bit (leaving my PC on) and a few hours later, when I got back I saw my screen was completely frozen, I couldn't move my mouse or anything. So I did a hard reset... and now it looks like my OS is not booting up.

I don't know if the update had anything to do with it, and I honestly have not been checking if my C drive (OS system Drive) was running out of space. I really would hate for any documents on my C drive to be erased with having to do a full reset or fresh install... if there is anything I can do, I would really appreciate the help!