Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
As long as you're able to power it on and access menu/setup, you can go into the Account section of the menu, then you should find deregister or restore defaults to wipe it clean.
That usually indicates the nook is hardware locked, which is a typical restriction for a store use device.
Plug the nook into computer via usb cable, then press and hold power button for 60+ seconds, and release. The nook will take 3-5 minutes to reload it's internal firmware. If it doesn't turn back on by itself, press power once to turn it on.
If that still doesn't work, then the nook is locked down. The only way around that is to "root" it, meaning to hack the firmware and install an aftermarket operating system.
Should it come to that, you're really better off just returning the nook to the seller on ebay and starting over.
Personally, I'd recommend a Kindle rather than a nook. They are much better supported, have a wider range of content/apps available, and are just more reliable hardware overall. You can get one for the same price, and there is even a nook app you can use if you have existing b/n books you've bought. http://amzn.to/1OEJZan
You're welcome, and best of luck to you!Nathan