The permissions for the drive might be damaged, try this:
Originally Posted by HuxJr
Right-click on Local Disk (C:) > Properties > Security > Advanced > Change Permissions.
Click SYSTEM > Edit and make sure all the permissions boxes are ticked (not the one about containers).
Ensure that Type is set to Allow and Applies to is set to This folder, subfolders and files.
Click OK and repeat the same thing for Administrators.
For Users, repeat but when ticking the boxes, do not tick: Full Control, Modify and Write.
Click OK and then OK.
Reboot, see what happens.
If it still doesn't work, attempt to run Command Prompt and execute the following commands:
That will reset all the NTFS permissions on the drive.
CD /D C:
icacls * /T /Q /C /RESET
System Restores makes a backup of all the security settings on the drive(s) and it's possible that it was corrupted or failed to restore correctly, giving only the OS full access to the entire drive.