Q: What could be causing my car to not start? on 1999 BMW Z3

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
I just replaced my battery with a brand new one in November 2012 and today my car would not crank. It wont even click over, it just seems completely dead. We tried to jump it off but only the lights come on and it won't crank, we've even let it charge from another car for about 20min and it still won't start. Could it be the Alternator or Starter? My friend told me it might even be the battery cables. And if it's one of those do you know an estimated repair price? I'm an 18 year old girl and I know nothing about cars, so any help is appreciated! Thanks.
(1) Answer
A possibility is the ignition switch,not the part you put your key in but the electrical part behind it that sends voltage to the relay and starter.They are known issue with BMWs.Have someone check voltage at the starter while you turn the key to the start position.And while they are down there have them tap on the starter with a large wrench,if the starter is faulty most of the time tapping on it while you turn the key will get things cranking.good luck,let us know what you find.