I'm reminded of the story about the guy who's car wouldn't turn over one morning. He immediately made the assumption that his starter motor was bad.
He got a ride to the parts house, bought a new starter, begged a ride back home and spent most of the remainder of the day installing it. Hit the key and nothing. So he figured his alternator was bad.
Another round of calling friends and another trip to the parts house and another half a day later he had a brand new alternator installed. Hit the key and nothing, again. Must be the voltage regulator.
The guy jumps through all the hoops again to get the voltage regulator replaced and, thinking that it's gotta work this time cause there's nothing left to replace, he turns the ignition key and, you guessed it, nothing. Frustrated to tears, he walks down to the corner bar, plops down on a stool, socks down a few doubles and lays his tale of woe on the long suffering bartender who looks at him like the idiot he is and asks, “Did you check the battery?"
Sometimes it's best to start at the beginning.