Not an easy solution I'm afraid! The software available for the PCM (Porsche Communication Management) system on this car is incompatible with your navigation computer. As such you would need to purchase a new navigation computer, together with new software (Which is supplied by a company called Navtech), which should be current standard.
The thing is, the cost will be well over a thousand pounds at least!!!!
Your local dealer will have more info.
The chances of you coming across software available for yours is slim. It will also be out of date, as the new navi computer came in in about the year 2001.
Jonty the Porsche man, June 2009