I got an ad-supported version Kindle 4 as a gift, but the ads bothered me, so I’ll show how to remove them.
Before we begin: Sometimes my Kindle fails to be recognized as a storage device. The workaround is to hold the power button for 30+ seconds to do a facory reset. This of course wipes all the data on my Kindle, but I keep all my books saved elsewhere, so I’ll just load them back and I’m good to go. The “documents” folder on the Kindle is the one which stores the books.
And now, the ad removing part.
Connect Kindle to PC, so you can browse the USB storage of the Kindle.
Open the Kindle drive in your computer.
Make sure hidden files can be seen by enabling the “Show hidden files, folders and drives” and disabling the “Hide the “Hide protected system files” option in Windows folder options.
Open the “system” folder in your Kindle drive.
Right-click an empty area and choose New > Text Document. Create a text file named “whatever.txt”. The name does not matter at all.
Go back to the Kindle drive, hold SHIFT on your keyboard and right-click the “system” folder.
Choose “Open Command Window Here”
In the CMD window, enter the command “ren whatever.txt .assets”. This renames the whatever.txt file to “.assets” a hidden file on the Kindle which stores the ads. Now that we replace it with an empty text file, no ads can be accessed by the Kindle.
Open the system folder again, and right-click the .assets file, choose Properties.
Place a checkmark on the “Read-only” option and click OK. With this step we make sure tat the Kindle won’t be able to re-create the .assets folder and download new ads into it.
Eject your Kindle and disconnect the USB cable.
Your Kindle is now ad free.