This is what I would do -- Prepare a basic Clockworkmod (CWM) bootup card as described in 1a of the first post at this thread:
http://forum.xda-developers.com/show....php?t=2062613
It's really easy. I've done it dozens of times.
Then insert the card into your dead HD and plug in the charger. Leave it plugged in for at least an hour or so, then press the power button and try to boot up into CWM. If you can, you will be able to charge your device for a few hours, then exit out of CWM.
If you can boot into CWM, you can then put a stock ROM on the card, reboot back into CWM, and flash the stock ROM from there. If successful, you should be able to boot into your Nook normally. It will be like a new device and you will have to register again. You will of course lose all your previous data.
There are links to the stock ROM in that first post in that thread.
--Pat