To change voice simply use NavCoder and select which 3 of the 7 standard language you want loaded. You can also ensure the Mk4 is coded for your vehicle at the same time

Get NavCoder here:
http://www.siegenthaler.co.nz/NavCod...s/NavCoder.zip

As for loading a special splash screen OS, remember that the nav will only load a new OS if the version number is different from the currently loaded OS.

Have a look and see what version is on the M5 board OS disc and compare.