Need help with windows which strangely reset itself.?

Hi, Today in the morning I booted up my pc. After it started up, it took a long time to load the desktop after I chose my user profile. When that was done, I got an error message that said some inf file is missing. Because of that, windows got reset or something and now it looks exactly like a fresh copy of windows with the windows tour popup and e.t.c The only other thing was most of my installed apps still had their shortcuts on the desktop, and some of them didn't. The wallpaper and all my other settings have also been reset, and I can't use system restore for this either. What the hell just happened?