Two reasons this could hav happened to you:
You updated your ata storage drivers from intel.
You accidently disabled DMA mode in bios.
For solution to 1:
Goto My Computer/properties/hardware/device manager/IDE ATA/atapi controlers…
Look under all three listings…Master controller and the 2 ide channels.
Look at your driver date… should be the one that came with XP 7/1/2001 version 5.1.2600.0.
If it is dated in 2002 then you updated your intelata drivers from intel and that is a no no. Roll back your drivers under all three listings using the xp roll back feature under the properties/driver tab of all three listings and you can choose your “DMA if available” option again under each of the 2 ide channel listings (Primary & Secondary).
I accidently did this to myself and lost my DMA on my slave channels. Rolling back the divers under ALL three listings brought it back for me (Master & Primary/Secondary Channels).
For Solution to 2:
If this is still not working, look in your system bios and hunt down to see if you disabled DMA by accident.