How to remove DRM from Kindle books

First things first
Before you start you'll need to download the following things
1. Calibre
2. The latest version of Calibre unDRM Plugins.
3. Kindle4PC. The official Amazon Kindle4PC software.

Setting everything up
1. Install Kindle4PC
2. Install Calibre
3. Unzip the Plugins for Calibre file. Open Calibre, go to Preferences, then Advanced, Plugins, on the bottom click Load plugin from file. Browse to the folder where you unzipped the contents of the unDRM Plugins, then select K4MobiDeDRM_v04.7_plugin.zip or similar. This is the file that contains the plugins for removing DRM for Kindle books; you may want to install the other plugins as well if you are planning to remove DRM from different formats, although for this guide they are not necessary. Press yes if you are prompted by a are you sure message.
4. Restart Calibre

Removing DRM Protection
Ok, now you are ready to begin the actual process of removing the DRM from the file.
1. Buy a book from your Amazon account. You have to have Kindle4PC open to synchronize and to download the file you want to remove the DRM from.
2. Look for the file you downloaded, it should be an azw file. The default download folder is usually located in ~My Documents/My Kindle Content for Windows or ~Documents/My Kindle Content for Mac.
3. Open Calibre, select add books and look for the file you are removing the DRM from. You can also drag the file directly into Calibre
4. Wait for Calibre to unDRM your file. You should now have an unDRM mobi or azw3 file. This is the file you should upload straight to the tracker to be considered retail. Do not convert azw3 to mobi or viceversa, whathever the format you obtain you should upload it without any changes.

Problems you may run into
Luckily, by following the steps above you now have a mobi or azw3 file that you can readily use. However not all books are in mobi or azw3 and you may end up with one of the following formats.

• HTMLZ When you end up with this format after Calibre removes the DRM protection, this means the azw file had a topaz file instead of the usual mobi file. The topaz format is unique and cannot be converted effectively to mobi. When Calibre converts this format to mobi or epub the formatting usually gets messed up a bit. I haven't found a way to deal with this problem, your best bet is probably convert to epub, though in some cases even then the formatting will not be the ideal. If you do this the file is not considered retail.
• Removing DRM from rentals Try using an older version of K4MobiDeDRM, such as 3.6.
• azw3 In some cases, you end up with an azw3 file. This is perfectly fine and can be readily used, what follows is just a description. This is a hybrid format consisting of KF8 optimized for new Kindle readers but also includes old mobi data which allows old Kindles to read the file. Upload the unDRM azw3 file whenever possible. If you convert it to mobi or epub, it is no longer considered retail.
• azw4 This format is common for Print Replica books. This is essentialy a PDF file wrapped in a Kindle file format. You will need a plugin called mobi_unpack to extract the PDF from the azw4 file.

Leave your comments and suggestions below. I'll update the tutorial accordingly.