How to reboot/cold restart a Kindle
If you want to unfreeze your Kindle or restore the factory defaults, do the following:
1. Hold the power switch to the right for 20 seconds.
3. Nine times out of ten just hitting the DEL button at this point will unfreeze your machine without having to lose all your files (please note, you can replace them later but it takes time and you will lose your notes, bookmarks, and settings).
4. If that doesn’t work you will have to restore the factory default settings by typing in R E S E T. As soon as you hit the T it will reset.
That’s it. Please note that this is for the Kindle 3G + wifi 6 inch version.