okay, to close this argument, there is no way that u can use the fm reciever in the htc diamond to transmit your music to you cars fm frequency, but there is a way to make your music play through ur car
get the headset adapter that came with the phone and plug in a two way jack, then connect it to ur 3.5mm headset jack in your car system, music plays fine through mine
hope this helped, and all of you need to stop being asinine
