Maybe this will add a little perspective
If you had to guess, how many computer instructions do you think go into making the Windows operating system? Would you believe there are BILLIONS? That's an extremely large haystack to sort through to find a missing needle. You could spend months and months trying and never find it. That's why experts suggest reinstalling. You can do that in a couple of hours. Granted, it could take several days after that to get everything back like you want it, but believe me it's still a whole lot simpler and easier than sorting through BILLIONS of computer instructions trying to find what's wrong.
What's the solution? Experts will tell you the answer is BACKUP. That's the ounce of prevention. Since you didn't do the ounce of prevention, you're now faced with the pound of cure. Sorry.
When you've gotten your system back like you want it, I urge you to get yourself an external hard drive and a good 3rd party backup program. You can set it up to do everything automagically at the time and frequency of your choice. 1 TB external hard drives are about $70 these days and a really good FREE backup program is the Easeus todo backup free which you can download from
http://www.todo-backup.com/products/home/free-backup-software.htm . That can save you a lot of time and frustration the next time something like this happens. Sooner or later it happens to all computers for one reason or another.