I often need to shrink NTFS volumes so that I can transfer all content to a somewhat smaller drive. To do this, I need to clear the higher sectors on the disk, moving as much as possible to the lower sectors. Optimize at boot-time will accomplish this, but it does so very slowly. A feature that would just move everything down (packing as tightly as can be done quickly) without defragmenting or optimizing would speed up the process significantly. Defragmentation can then be run after migration to the new drive.