I had this "won't enable dma" problem on my old computer. Easiest way for me to fix it was to a) go into control panel>system>device manager and delete the driver for the cd burner.
Then, reboot and windoze will reinstall the cd burner drivers. Next, confirm that the cd burner is set to DMA. If so, you're all set and things should burn right quick.
It's important that nothing else be on the ide channel for the cd burner.
Once drivers are set up, you should have no problem burning @ 52x on a p3. I had none on my p2-400.
Darrin