Do you have a Windows 7 "system image" backup you can simply restore to your C-drive?
Do you have a "system restore point" you can possibly try restoring?
If/when you recover (or end up reinstalling from scratch and starting over), you should plan on a systematic daily/weekly/monthly backup regimen of automatic backups taken at regular intervals, probably using 3rd-party software. You'll never lose anything again.
I use Macrium Reflect Standard
to do my weekly "system image" backups, rather than the Windows 7 equivalent. Macrium's product is much more flexible, powerful, and user-friendly, and comes in a free version as well as an inexpensive "standard" version whose additional features (specifically "space management") I found well worth the small price. But the free version works fine for many users.
I use non-free NovaStor's NovaBackup product
to do my monthly "full" backups and daily "incremental" backups, backing up all of my data folders/files on C as well as my other partitions D-M, but ignoring the \Windows folders/files as they are very large, and also unnecessary for a "data backup/restore" plan when "system images" are also being taken as I do.
Note that Macrium Reflect also supports the exact same type of "data" backups that NovaBackup does, so you can actually buy Macrium Reflect Standard and use it for your complete backup scheme. I just prefer NovaBackup because (a) it supports backup to tape which I require, and (b) has a simpler, more basic, and more understandable user interface which I actually prefer.
I know this is no comfort or solution to your current problem, but without a recent "system image" you can immediately restore, or at least some "system restore point" you can try to see if that fixes things, you may be doomed to have to start over and reinstall Windows 7 from scratch.