My 2002 X5 did not have any aux input on it, so here is how I set it up to play my Iphone in it.
I went to the apple store and got a simple casset player adapter.
But since I hate cables dangling down the dashboard, I had to hide it.
I removed the radio head, and efd the cable down to the cigarett lighter compartment, put the radio back and it works perfectly.
Cheapest easiest way to play your mp3 on the radio without interference.
I hope someone finds this usefull.