In XP go to Control Panel... Performance and Maintenance... System... Hardware...Device Manager...
Click on the IDE ATA/ATAPI Controllers to see a list of your Primary and Secondary Channels. Right click on each and select Properties... Under the Advanced Settings check to see if the Transfer mode is set to DMA if available and that the Current Transfer Mode is NOT PIO. If it is PIO Right click the drive channel in the device list and click Uninstall! This might seem a LITTLE RADICAL, but it will fix the problem.
After you have uninstalled the drive channel, Windows will want to Restart your computer. During that time, it will reset to a DMA setting in most cases. If it does not, then you are stuck with PIO.
I think that my DMA problem was created when I installed a second hard drive. Oddly the Primary was PIO and the newer drive was already set to DMA.
Give it a try! It worked wonders for my sound and the darn thing runs a little faster too!