I'm not sure its worth the hassle/work required to make it work. There aren't any free GPS routing packages which are actually any good or have the required maps available. Your best bet for free maps would be something that used OpenStreetMap but there aren't any guarantees that the data is accurate.

If you do get a third party package which costs money then you might as well just buy a brand new cheap GPS unit...

If you really want to get it working and are willing to spend some $$$ then look into TomTom. They had/have a WinCE version.