PM sent. But...
There should be three partitions on the internal SD card. Two will be ext3/4 and the third it FAT32. The first two should be 256MB in size and the third the rest of the disk.
When the device is plugged into a PC, only the FAT32 partition is presented to the PC. The other two are completely hidden. Removing the card and putting it in a Windows PC usually gives errors as Windows doesn't like multiple partitions on removable media and two of the partitions are formats it doesn't understand. If you put the card in a Linux machine, it can see and mount all three partitions. I thought a Mac would be the same, but have never tried.
For restoring the image, I usually point to
Memory Upgrade Mod Guide. That suggests "Flash Drive Image Writer" for writing the image.