Arduino Mega only recognized as Marvell 91xx

I'm having the hardest time figuring out how to install the drivers for my arduino Mega adk. I'm starting to think it might have arrived with a dead processor. The on light glows, and the LED with an L next to it is lit. I tried a few months ago to install it on a Windows 7 computer with no luck, and gave up. Now that I have some time, I am trying to install it again, but this time on Windows 8. I followed the instructions to allow unsigned drivers, but the device is still recognized as Marvell 91xx, and not any arduino board and I am unable to follow the driver installation instructions.

Has anyone had this problem, or has any suggestion on what I should try to get it working?