Make sure everything is set up in your BIOS to allow DMA mode when available (on Award bioses, I just set the controllers to auto detect and that usually works, but you may have to set it to try to force DMA mode if possible)
Then make sure everything in the device manager is set to allow DMA mode when available. You'll know whether it's using DMA mode if it says "Ultra DMA Mode" for the first device on the primary controller... if it doesn't, you know where your problem lies and you should try the above suggestions, especially reinstalling chipset drivers.