How to add Defragment to the Right-Click Menu for a Drive

After manually applying or downloading the hack, you’ll have a new item on the right-click menu for your drives…

Which will start up the command-line version of Disk Defragmenter (after accepting the UAC prompt)
 
Manual Registry Hack
Open up regedit.exe through the start menu search or run box, and then browse down to the following key:
HKEY_CLASSES_ROOT\Drive\shell

Create a new [...]