It's possible that something has been corrupted in your OS. It could either be software level or hardware level.
Could you run (any of) the following in command prompt with administrator privileges?
1. sfc/ scannow
2. chkdsk
3. chkdsk /r
Option 1 checks for errors/corruption in the OS at the software level and then automatically attempts to repair the errors it finds. Option 2 quickly checks for bad sectors in your hard drive (usually detects those with severe bad sectors, not minor ones). Option 3 checks every single sector of the hard drive and attempts to repair the corrupt sector, recover the file in that sector or mark the sector such that it won't be used by the system anymore.
Option 3 takes a LOT of time, so if nothing comes up in options 1 and 2, you may go with option 3 but choose to a time when you can leave it running for several hours (mine took 10 hours).