ClaudeP: You have done everything you can to get it going. By the sounds of it, it had already been messed up by the previous owner.
You should be able to get it going by restoring an image to the SD card. Using a new one is a good idea in case the other was faulty. I have sent you a PM with the link to the image. For instructions, see
Memory Upgrade Mod Guide (With Pictures). You already know how to open it, but it has the instructions for restoring the image and links to the tools needed.