Fuse Blowing after new CD Player installed

Hi there, one of my friends has just installed my new Pioneer CD player but now i am having troubles with the light on my instrument panel and air conditioner.

I found a fuse that has been blown, and replaced it and it blew again when i put the lights on. Also the warning tone to remind you to turn your lights off doesn't come on (I assume this is because of how the circuit works).

Does anybody know a problem that could be occurring with this?

Well, aparently the problem is that you have a short somewhere. The only way, really, is to test all the relevant wires in the affecter circuit.