1. Download the recovery tool for your Fritzbox. This can be found on the AVM FTP server ftp://ftp.avm.de/fritz.box/. Once on the AVM FTP you will need to navigate to the directory that relates to your fritzbox. Now navigate to the x_misc folder.  Next select the correct folder for your language. For me this was englisch, the type-o is on the FTP server. Finally you need to download the executable namedFRITZ*.recover-image.exe where the * is the model of your Fritzbox, languages and firmware version, download and save this file
  2. Have a machine handy with WinXP, Win 8.1 gave me issues, boot up and have files handy 
  3. Skip this step if you have your own FTP tool and know what you are doing. Download PuTTY from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html you only need putty.exe but you can download the installer if you prefer. If you get the installer go ahead and install it now.
  4. Once you have both the tools you need to run the Fritzbox recovery tool and follow the instructions until you get to the point where it complains about the settings being set by a service provider. At this point you need to open PuTTY. On the right you will see an area for an IP Address, Port and Protocol. Set the Protocol to Telnet, enter the IP Address shown in the recovery tool and set the Port to 21.
  5. Now, after setting up PuTTY, click the open button at the bottom of the screen. This will now open a black console window. Enter the following commands:

     

       

    1. User adam2
    2. Pass adam2
    3. unSetENV provider
    4. Quit

     

  6. Finally close PuTTY and the Fritzbox recovery tool. Then open the recovery tool, again following the instructions. This time you should not be presented with an error about the provider and the tool should flash the Fritzbox.