Originally Posted by HarryT
I think you misunderstand me. I don't think there's the slightest issue with reflashing the firmware on a Kindle that you've bought in the normal way. It may perhaps be a technical copyright violation to download a ROM image from somewhere, but only the most anal of people would regard it as "wrong".
Where the issue lies here is that a Demo Kindle has never been licensed to run the retail firmware. Does the buyer have the legal right to install the retail firmware on it? It's a grey area, at best. It may very well not be legal to do so.
It is not so much the kindle HARDWARE that is at issue, but the kindle SERIAL NUMBER registered with amazon. That serial number may or may not be allowed to access the 3G network. If it does not work, you may be able to convince an amazon tech to register it for you, perhaps after paying an "upgrade fee". Because you can change the serial number (stored in flash), you could swap serial numbers with one from a broken kindle.
Another possible problem is that demo units sometimes contain defective hardware that is not used by the demo software. They need to do SOMETHING with factory rejects, after all... And the 3G modem card may be missing as well. You may need to remove the back cover to check.
P.S. I have noticed that some recent store demo eInk readers (Kindle Touch and Nook Simple Touch) do not even have an eInk display in them. They just have a sample screen printed on PAPER mounted behind the glass display surface.