well, a couple things: first, just because the engine will not turn over, it does not mean the batter is dead. It could also be your starter, or more likely (from what it sounds), your cable connections. So, first, double check firm connections at the battery on both terminals, and then, check you have a good firm connection at the ends where the battery leads connect. Then, if all is well, double check you have a good battery (using your battery charger/tester). If you have a good battery, and all your connections are good, then you may have a bad solenoid on your starter. Before changing your starter, be sure your cables are good and they are not broken or corroded.