Have a try...
Here is guide found on openatv forum HOW TO FLASH.
You want to use another SD card card or E2 does not launch, here is the solution:
Preparation:
1) Prepare USB stick, format with FAT32
2) Download the image from here. openATV Nightly Downloads
3) Unpack the file and copy the dinobot folder to the USB stick
4) Insert the USB stick into a USB port on the side.
5) Switch on the box and if the display shows "Menu", press the green button on the remote control
Now the image is installed as shown here in the video: