Since it seems I was the one that originally started this craze, it's only fair that I answer.

Here are a few notes, speaking from personal trials (yes, I was brave enough to try on my OWN nav computer)

1) No, you cannot "permanently" screw up your nav computer with a corrupt image. If you screw up the checksum with an invalid GIF89a image, the disc will either NOT boot, or will boot and hang during the middle of the install

2) Dont panic, turn the car off. If you have a video module, when you turn the car back on, you'll have a very rudimentary main menu. Eject the disc from the nav computer, and insert a FRESH copy of v26. Give it a few MINUTES (not seconds). It will eventually boot and load the fresh copy of v26 back onto the computer. Then you're free to go back into the house and continue hacking the OS LOL

DISCLAIMER: Just because I've flashed mine about a ZILLION times and not killed it, doesn't mean you'll do the same LOL

Now, for the other news.

I have NOT changed the logo, but I have been able to successfully REMOVE it from the code.

There is indeed a checksum, however, we need a Microware OS-9000 guru to figure out that portion.

I have a copy of IDA PRO if anyone needs it (with the OS-9000 plugin)