NOTE: I completely not responsible for any damage you got from doing this. I got this from internet source and you should know it all at your own risk. But i clearly tested it and it work like a charm!
You just need a simple script to add to your windows registry. On this situation, i tested in Windows 7 Ultimate
Simply copy&paste this whole scipt and save it as "name.reg"
Windows Registry Editor Version 5.00
;Show 'open command prompt here' on right-click without having to press shift
;Context-menu for folders
;Context-menu for drives
;For context-menu when you right-click in the empty/blank space within a folder
###End Of Script###
Open your notepad and copy&paste this whole script and execute(double click) it and select yes if you asked by system to add this value to you windows registry.
If you consider this action is such mistake and want to recover it back, please read "how to remove" here