What “trysesfirst” said - Install the driver, I think you can download it from WD.
I’ve had this happen as well, XP sometimes just does not detect USB drives. You may need to check Windows Update for any Driver Updates for your motherboard. Also if you have insufficient Chipset drivers in your OS it may do this as well.
Usually this happens to me with the Laptop Sized drives, the ones that have no power adapter. I’ve never heard of it happening with My Books, but the SES thing may be valid, so try that.
