Hi,
some people had problems with installing python and running the script so
I converted the python script that is floating around in these forums to JavaScript. If you need to calculate your Kindle's root password and it is running firmware 4.0.1, just go to
http://members.ping.de/~sven/kindle.html
The calculation is done completely in your browser, your kindle's serial number is not transferred anywhere.
Perhaps someone can add this link to one of the sticky threads here?
Anyway, enjoy!