Stylus? Hehe, it isn't an old vinyl player, it uses multiple magnetic heads on several spinning discs.
Anyway, I'd move 400mb to the other drive, defrag the first and then move the 400mb back.
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn!
"The sky was the color of a TV tuned to a dead station" - Neuromancer