Electrical problem?

My BMW won't start without a jump unless I remove one of the contacts from the battery. I assume there must be a draw somewhere - is there anyway to test this? It may be the aftermarket cdplayer - but that was installed with a wiring harness, so I don't think that is it, but nothing else has changed.

Any advice? (92 318is)

It could just be a bad battery, that can not hold a charge. It could be the cdplayer, just unplug it for a day. It could be as easy as a light on in the glove box or a short in the wire some where. Start with them two things first...