You can also use the key below to activate your Windows 8 Professional.
Product Key: TK8TP-9JN6P-7X7WW-RFFTV-B7QPF
Make sure Windows Updates are set on never check for update, As update is not useful. it occupies hard disk space and makes machine slow.
This activator has been tested on Windows 8 Professional, and should work for other versions also. Leave a comment here if it doesn't works or you have any questions.