I believe that DMA is enabled by default on Win XP installations - provided of course that the hard drives are capable of operating in DMA mode - as most modern drives are....
All my 'XP' PCs have DMA enabled and I have never deliberately set them up in this condition. If I remember correctly, earlier versions of Windows required the user to select DMA operation, if it was required.

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Willum
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Willum

After silence, that which comes nearest to expressing the inexpressible is Music.
Aldous Huxley
( especially when the music is played on a KN7000....)