Ok, I don't know how this turned into a thread on grub.conf, but getting back to the subject...
Many IDE controllers are buggy, and can corrupt your hard disk if you use DMA. To protect against this, linux uses PIO by default. If you're sure that your IDE controller does not have this bug, you can turn on UDMA and high speed using the hdparm utility. man hdparm for more info.
Apologies if this has been answered before.
Philip