What To Do If Deleted Registry?

I was using the RegCleaner and clearing out some unused keys made by programs i no longer had on the computer.It was simple enough and nothing going wrong, no harm done. I went to go take a piss and when i came back i found my buddy on my PC.He asked "what the H*** is all this??" and i said "its my registry" and he goes "o you dont need any of that" and no sooner did those words come outa his mouth did he press Shift + A & DELETE and poof..all my reg keys were gone.i dunno if i have a back up present.what i can say is that every time i try to click on something now it says its either been moved, deleted, or renamed..nothing works anymore besides my internet. i cant even run .zip files because it says there is no program to do it with. theres no program to "open" files with. all because my screw up friend over here decided he knew what he was doin with my pc.