First thing, rather then me typing a bunch of redundant information go **Here** And Follow the instructions, this will get you started. After doing that the MMCS hard drive should be removed from your car and you should be able to access it from a computer. ** I would recommend making a backup of the entire Hard drive before screwing with anything. ** This can destroy your HDD and no GPS, Music server or any other function will work if the hard drive is damaged. ** You will notice you have 6 partitions, a couple of them are completely blank, the others have the files for the music server, GPS, bluetooth and other functions. If you wanted to put in a larger hard drive all you would need to do is image the drive over to a larger one and simply size the partition with the Music server data onto a larger partition. Find the partition that has the bootup image and you can edit it or simply replace it with any other gif. The only limitation I've found so far is the size (resolution) of the image, it needs to match the existing size on the file. And backup all files before you replace anything. I've done this multiple times and I have my own custom image on bootup, I can answer any questions that you may run into.
