[chyron8472]

How are you transferring the books? Are you going into the My Kindle Content Content folder (the folder where K4PC stores ebooks) and copying the files from there onto your Kindle? Are you importing the files from said folder to Calibre and then sending them from there to your Kindle? It sounds like you are. These methods won't work with DRM'd books.

It sounds like your Kindle is complaining that the DRM for the ebooks doesn't match up with the PID for that Kindle. What the error message is telling you to do (and what I suggest) is that, if the ebooks in question were bought from Amazon, you ought to redownload them from Amazon on to your Kindle.

This is possible in one of two ways:

First you can select the books in question from within the Archived Items section of your Kindle (you must have 3G or Wifi on for it to work) which will redownload them from Amazon to your Kindle for free.

Second, you can send it to your Kindle from your Amazon account on the web. In your Amazon account, in the section that says "Digital Content" click on the "Manage Your Kindle" option. On this page, there is a table which lists all of your Amazon ebooks. From here you can choose to upload your ebooks from Amazon to your Kindle (again, you must have 3g or wifi enabled) for free, or you can download the files to your computer and copy them via USB.

The fact that you can download them to your computer and copy them sounds redundant since you have them on K4PC, but it's not. If you do select the option to download them to your computer, Amazon will then ask you which device you're planning on transferring it to so it can tell the books DRM which device to associate with.