Won't mount as an USB?
One of the biggest downsides of buying into the Apple empire is the fat, bloated toad which is iTunes. Insisting on the use of Zune in the same capacity is a massive mistake in my opinion - you are not going to out-Apple Apple in the walled garden approach.
Some interesting approaches Microsoft, but I think you are barking up the wrong tree and targeting a converted market. A shame really, more competition in the mobile OS market is always good.