The Nokia N91 mobile phone certainly has the 'wow factor'. It's a music-playing mobile that can store up to 3,000 songs and can take photos in two megapixel quality. Okay, let's look at that figure again. Three thousand songs. Or, if you prefer, the equivalent of playing non-stop music for a week without listening to the same song twice. How on earth can you fit all that on a mobile phone? Simple - just include 4GB of...