UPSer :
It is indeed in PIO Mode, and will not change to DMA.
Perform the following procedure:
1. Update Windows XP to SP2 if you haven't done so already.
2. Make SURE the IDE cable you're using is an 80-conductor cable (blue connector for motherboard, black and gray connectors for devices), and is NO MORE than 18" long. If your cable doesn't look like this, trash it and get a correct cable.
3. Go into Computer Management, and click on Device Manager.
4. Expand the IDE ATA/ATAPI Controllers node.
5. Double-click on the IDE controller that contains the hard drive that is stuck in PIO mode.
6. Go to the Driver tab, and click Uninstall to remove this IDE controller.
7. Restart the computer. Windows XP will reinstall the IDE controller during the restart.
8. After the restart, go back into Device Manager and verify that the IDE controller is reinstalled.
9. Run regedit, locate the following key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0001
You may see more than one key under this node, you will have one for each IDE controller. For example, there might be:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0002
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0003
etc.
10. Inside each of the 0001, 0002, 0003, etc. keys, do the following:
Create a new DWORD value named "ResetErrorCountersOnSuccess". Set the value to 1.
11. Restart the computer.
12. Go back into device manager, make sure the offending hard drive is now in DMA mode.
The .vbs program that nukemaster posted essentially does the same thing.