The 2007 BMW X5 does have Bluetooth, but you can only use it for making and receiving phone calls. Music streaming through Bluetooth wasn’t available in BMWs until a few years later.
Nevertheless, you still have a few options if you want to stream audio from your phone to the X5 stereo system. **You can either buy a Bluetooth car kit that bypasses the original BMW system and lets you use your phone to stream music, or, if the car has one, you can connect your phone through an auxiliary cable.