Hmm sounds a bit complicated to me. This is a link to a win CE device I modified some time ago.
http://www.gpspassion.com/FORUMSEN/topi ... C_ID=44304
The process was made easier due to my PC being hooked into the device via it's usb port! Basically we stopped it booting up into GPS mode, then installed Tomtom and then made it boot up in Tomtom.