I've gone a little further than our friend atomantmk with iGO for the PC
http://www.navitotal.com/forums/showthread.php?7130-iGO-for-PC Here is the working program direct from my PC.
NOTE[S]:
1. The voices are non-TTS [both English US and UK]. I can't get the TTS to work just yet but I'm still playing with it.
2. Unless your PC has an external GPS antenna, the program will only work right now either navigating a simulated or fly-over route.
3. There is no geographical content - add your own.
If you get TTS to correctly work, please post how you did it. Thanks.