I forget the exact egistry location, (I found it with Xsetu (
www.xteq.com)
I added a right click explorer context menu popup to run contug on files. This way you can "Right click>defrag" specific files.
Really handy as I deal wit very large video files all the time and I like to defrag tehm specifically. Using this method too you can highlght a group of files and defrag them all.
In Xsetup the locaiton is something like "appearance>explorer>shell"
The comand i put there was c:\contig.exe "%1%"