windows registry error

I am very confused that this windows installation still even works. Not even commands work correctly. Windows defender is fucked up and integrity is non-existent. But I have an idea, I always have an idea. But I don't know if it does the correct thing for my problems. I want to reset windows...

this problem has started awhile ago I don't know what caused it, but whatever it is it has either deleted, or corrupted the sound drivers on my computer, because whenever I try to use the Audio service on the my x64 Windows 8.1 Dell Laptop it just pops up a Detecting Problems Box, and the Audio...