This is the link to the main Kindle Software Update Page:
http://www.amazon.com/gp/help/custom...deId=200529680.
There are separate updates for each Kindle model. You MUST download only the update that matches your Kindle model. You can confirm which Kindle model you own by looking at the first 4 digits of the serial number located on the back of your Kindle and comparing it to the serial number(s) listed with each update.