A cheapskate like me likes the freebies----I have been using dklite--but it does not defrag in the background.
I have tried dims but its a registration nighmare.---I am now playing around with the iobit smart defrag beta which at least defrags in the background---but as a beta has a few bugs---the main one being it can screw up windows shutdown--which is easily cured with a mouseclick--just right click its icon on the taskbar---select exit--and then shut down windows.---but iobit
is working hard to get it right---with new versions coming out almost monthly.---and they are talking an implementation of hyperfetch for win XP.------so try at your own risk.