I can't say I know who is the maker (really, the OS and build) of either the nav on the Toyota or the GM, but, simply putting some random file that works on one in the other is not generally going to do anything. Again, it depends on the nav itself, but, just an example... boot.ini is part of the boot loader for Windows and boot.efi (I believe) is the part of the loader for Max OS X. Replacing boot.ini with boot.efi (or vice versa) would likely cause the machine to not boot into either OS, but simply including one file or the other in the boot directories while leaving the original file, would likely do nothing. If you still want to try it out, like stevek said, you probably (depending on age) have a warranty, though, electronic warranties are... tricky (in my experience).
