In Europe, Microsoft have Autoroute, which as well as being useable on notebook, is also useable on Pcket PC or some smartphones too. It is also quite cheap. I see that you are in OZ, but Microsoft will most likely offer this software under a different name in that market.
If you are going to have to spend money on Nav software, I would Google like mad and read as many reviews as you can before parting with cash. There is a gulf between some of these packages.
Conan