Incomplete defrag

Microsoft Windows XP

Defrag ends at 4% and no amount of re-running makes any difference. Does
anyone know the cause of this and how to get it to do a complete defrag?

Thanks.

Bill Ridgeway
Try booting to safe mode (Restart > press F8 when the black screen appears)
and then defrag. Drivers and running programs could be interfering with the
process.