DVD drives revert to PIO mode

They should ordinarily be Ultra DMA but they revert to PIO. The results? Massive CPU usage while playing a CD/DVD, especially when burning DVDs. If I burn a DVD while the drive is in PIO mode, the result is the buffer level being incredibly jumpy and my whole computer being so unbearably slow that I have to leave and come back when the burn is complete.

I don't know what causes it. Supposedly after X many failed reads, Windows turns back to PIO mode. There seems to be no way to stop this - besides not playing any media that might cause read errors, I guess. There are several methods to work around this, like setting the drive to reset the error count after one successful read. This worked for me once, it's not working anymore.

I've uninstalled the Secondary IDE Controller from Control Panel, uninstalled the drives, etc, and rebooted. Doesn't work. I've checked BIOS settings as well, which wasn't helpful.

But I need to be able to burn DVDs. Does anyone know anything else I can do? There needs to be some way to force Ultra DMA, but I can't find anything through Google.

Jam it back in, in the dark.