I'm using USB on a different board, so I don't know how much help I'll be, but let's give it a shot.
First, what version of the OS are you using on that Dell?
Second, with the board powered up, when you connect the USB cable to the Dell, does Windows XP chime, signaling that it it recognizes that a USB device has been attached?
Yeah, simple questions, but we need to confirm that the USB interface is actually working, particularly when the error message hints that it isn't.
---Tom