Patching Issues (WoW)Follow

Ive been away from WoW for awhile and I planned on coming back. I tried updating my game with all the missed patching. I was on patch 1.8 and it succesfully download, but 80% into patching i got

ERROR: unable to apply patch to file 'World\Maps\Zul'gurub\Zul'gurub_37_53.adt'

It also states that I should try Reinstalling my WoW. This is where the problems is. I cant find my CD key. So im wondering if there is a way to solve my patch issues without reinstalling. If not, is there a way to get a legit CD key without purchasing a new WoW.

Yea my dumb self just figured it out by going ahead and reinstalling anyway. Its been a long time kinda so i couldnt remember. Thank you for the response.