Recovery Mode is a special mode allowing direct access to the reserved partition of the Sansa’s memory, for repair of the firmware. The “main image” referred to in the error message is the firmware.
Be very careful that you DO NOT ATTEMPT USING THE WINDOWS FORMAT COMAND ON THIS PARTITION.
Download the two firmware files in the beginning of this thread, unzip them, and place the pp5022.mi4 and BL_SD files on the desktop.
On the Sansa, start with the device OFF. Slide the HOLD switch atop the device to the right (orange showing). Press and hold the REC button on the side, keeping it depressed while plugging in the Sansa to the USB port.
Open a Windows Explorer window by going to My Computer or use the shortcut [Windows Key] + E. You’ll se a new icon labeled 16MB FORMAT. Again, DO NOT attempt formatting this with Windows, as it will remove critical data. Double click on the icon to open the partition.
Drag and drop the two unzipped firmware files into the partition. Now, right click, and select eject.
Slide the switch back to the left (Hold OFF), and unplug the cable. Your Sansa will announce “firmware upgrade in progress”, and you will have a happy restored machine!