Porsche Boxsters and 996 are known for having issues with batteries running down when they are not used enough, we get asked a lot about jump starting a Porsche Boxster or jump starting a Porsche 996. This video is pretty good. Your thanks to the guys who made it. (we'll try and make our own soon).
If you have no power at all, you will need to jump the fuse box, there is a red connector in the fuse box you can put power to that will give the car enough power to open the bonnet (trunk). Sometimes you have to lock and unlock the car from inside to get this to work. Once bonnet (trunk) is open you can proceed with putting jump leads on your Porsche Boxster / 996. Battery is in the front of the car right up to the front bulkhead under a black plastic cover in the centre between the wipers.