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Windows downgrades the access mode of IDE devices when it encounters six disk errors. You end up running in the performance throttling PIO mode and setting the IDE device back to "DMA if Available" rarely sets it back to DMA mode. You have to do some work in the registry to fix this problem and prevent it from happening again.

Information gathered from http://users.bigpond.net.au/ninjaduck/itserviceduck/udma_fix/

In regedit go to:

 [HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\Scsi\Scsi Port 0]
 [HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\Scsi\Scsi Port 1]

Change:

 DMAEnabled = 1

Go to:

 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0001]
 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0002]

Delete:

 MasterIdDataCheckSum
 SlaveIdDataCheckSum
 MasterDeviceDetectionTimeout
 SlaveDeviceDetectionTimeout

Create:

 ResetErrorCountersOnSuccess = 1 (DWORD value)

Reboot.

You should now find the IDE devices in DMA mode. With the last key present, the device access failures is reset to zero after every successful access meaning that you would require six consecutive failures before getting another PIO failback, previously you only needed six cumulative failures.