In this picture you can see where the drive would normally plug in (that thing on the top right of the green PCB). Since a WD800 is also an older PATA drive it wouldn't connect even if you had the control board for it.
I'm also confident in saying that a Maxtor external drive would never ship with a WD drive inside
I wonder if someone took the 750GB drive out and then returned the external to frys. I don't think frys will help you though since you've had it for over a year and Maxtor/Seagate will likely assume you tampered with it since it's got a WD drive.
If you just want a working external, you can buy a SATA drive and put the enclosure back together.