Yes, it will simply operate at the speed of an Ultra DMA 33 drive. You can buy Ultra DMA 66 controller cards so that you can take advantage of the drives increased speed capability. Dennis www.citiesetc.com > Will a Ultra DMA 66 hard drive work in a system that is only Ultra DMA 33 > capable? TIA. The PCBUILD web site always needs good submissions. If you would like to contribute to the website, send any hardware tech tips or hardware reviews to: [log in to unmask]