Defraggler could optimize the system files that are read by the Operating System upon start up. These files/directories are listed in the file "C:\Windows\Prefetch\Layout.ini". So, DF should read all the files/directories mentioned in that file and put all the files/directories together in one place on the harddrive.
Or perhaps there's an Windows' API or MSDOS command available that allows DF to put Windows to work to do the task as described above.