Well if it runs ok in PIO mode but not DMA there must be some form of data corruption occuring between the controller and drive.
Usually this is cauzed by the IDE cable.
If errors are detected on bootup often windows will default the drive back to PIO mode, one of the main reasons why people complain of slow optical/hard drives.
Swap out the current cable and try another, even if its only a ata33 cable.
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