You didn't mention the dell model but if you are using a 2.0 device and the motherboard only supports 1.0 then it may not recognize properly. Should default to a lower speed but that has not always been the case. My USB 2.0 DvD drive had similar issues until I added a 2.0 PCI card.

I just read your post again. The software that comes with the HD would only supports IDE or serial? That's what you bought. The bytech box would have the USB drivers but they have the same drivers installed. Does the thing (box) have power? The USB IDE conversion probably does not have enough power to supply the drive if not. /edit sorry Tim didn't see your post about the power.