Microsoft's support for the Zune HD as a game playing device has been pretty abysmal. Luckily there are hackers, one of which has the beginnings of a serviceable Game Boy Advance emulator working on the device.
I purchased a Zune HD the first week the device was available, after my bother spent the better part of an hour showing me how gorgeous its screen was, and how fluid the menu scrolled. I justified the purchase by telling myself there would be games for the platform through Microsoft, and there were a couple. In November of last year, a handful of new titles were released, some which showed great promise, but ultimately this really isn't a gaming system.
Just don't tell the hackers that.
Yes, the Zune HD has been broken, and ZuneBoards user BackAtIt is hard at work honing Visual Boy Zune, a port of the popular Game Boy emulator Visual Boy Advance. His version currently only handles Game Boy and Game Boy Color titles, lacks sound support, and needs a lot of code tweaking before it's anywhere near fully functional. Still, it's nice to see the homebrew scene working to turn the Zune HD into a much more useful device - a Game Boy Micro.
WIP: GameBoy(Advance) Emulator [ZuneBoards via Engadget]