I think my favorite comment the moderators have is " you only lose that which has not been backed up " or something close to that. lol
At the point that your getting this message and using a restore point does not fix it then the next step would be to go to your backups. If you have not been making backups or you have just been making backups of your data and not the C drive then your only choice will be to reinstall the OS.
After the reinstall you should look into the imaging software that is available so you do not have to go thru this again.