Next time try unhooking the power feed wire to the alternator, that should kill any drain it may have. A clock, radio, computer, and alarm all pull power with the key off, but not enough to kill any decent battery, check the dome lights, trunk light, and under hood light.
Alternators are the only items big enough to drain a battery and still not catch fire. A starter might if the relay was stuck in, but it would be very hot to the touch and you would hear something from the starter.
one more thing, crappy cables will fool you, they can act like a dead battery. Check the connections good, at both ends!
Joe
