it reports an Arduino Mega 2560
It sounds like it is enumerating, which means it can't be that faulty.
Are there any special markings on the board which might suggest what it is, exactly (like, a web site)? Some boards come with their own device drivers. I think if you can get the device driver installed your problems will be over. I think I read somewhere it isn't exactly a "driver" but a .INF file that has to match the board's USB "signature".