To Open Registry Editor go to Start > Run
(or Press Windows key+R) and then enter
'regedit' (witout quotes) like in image..
Click 'Ok' Button or Hit 'Enter'
Then it will Bring Registry editor in front of you.
like below image



OR
You can go to My computer & type 'C:\WINDOWS\regedit.exe' (without quotes) in address bar & hit 'Enter' key