source: PCstats

WindowsXP always defaults to PIO transfer mode on the IDE channels, and not DMA? DMA not only allows for faster data transfers between hard drives and CDROM's but it also frees up a lot of CPU cycles! Luckily you can change the PIO setting very easily to DMA.
Right click on the "My Computer" icon and go to "Properties". From there click the "Hardware" tab and go into your "Device Manager". From there, expand the "IDE ATA/ATAPI controllers" and select either the primary or secondary IDE controller.

Once you've got one open, go to the "Advanced Settings" tab and under transfer mode select "DMA if available". You'll want to repeat this for the other IDE channel and you may need to reboot for these changes to come into affect. Once done, you should notice your data transfers are much quicker and you have a bit more resources available when doing disk intensive activities, or watching DVD's on a DVD-ROM.