you have to wait one hour with the dead battery before you try to recharge it. try that first. if that fails, you'll have to open the case to unplug the battery and the other connection in there in order to do the hard restart. which is what i had to do.
ok here is exactly what i did. when you have the case off of it, use your thumb nail to pop open both of the connections where the two ribbons go in, on both sides of the zune. then, first press down the short ribbon's connector on the left side, then press battery ribbon connector on the right side. once you do this, the zune should power up with the loading screen, then go to the main menu (but the d-pad will still be unresponsive for navigating). once you get to the main menu, you need to re-boot it with back+up. the zune will shut down, and begin to power up again. as SOON as the screen lights up, press and hold back, center button, and left all at the same time. this will begin the hard restart.
make sure you reboot it first because otherwise i dont think it will work. also, make sure your battery is pretty well charged before you do the reset, otherwise it will die in the middle of the reset. also, you cant have it plugged in while you do this.
so once you do the back, center, and left combo the screen will say that it's resetting or something like that, and it will take a few minutes to clear itself of all data.
once you clear it, it will prompt you to connect it to your pc. then you can re-install the firmware to the device. and finally you can put all of your content back on it too (which only took me about an hour)
let me know if you get stuck on any of these steps, and if it does or doesn't work for you. and if my directions give you trouble, you can go to
http://support.microsoft.com/kb/927001/?sd=zune
for a little more detailed directions on resetting it.