When your car won't start, and you hear no sounds, you are likely confronting a dead battery. A dead battery can be caused by a litany of things so we will take a quick look at what might be the cause, and also suggest some alternate causes if the problem does not lie in the battery. 1. Check the simple items. Check your headlight switch to insure you did not leave your automobile's headlights on overnight. Next, check any and all interior lights (including that back seat reading light the kids like to use.) If either of these have been left on you have probably found your culprit. If neither of these prove the root cause, once you get the car started again make sure to check for a bad trunk, under-hood, or glove box light that doesn't turn off properly. 2. Under the hood, take a good look at the battery while you're under the hood. If the terminals are "cruddy" or "dirty" (or loose) you may well have a bad connection. Also while you're under the hood, take a quick look at your alternator belt to insure it is in place, tight, and in good condition. Though a problem with the belt is much less likely the culprit, it never hurts to check. (Your alternator is responsible for constantly recharging your battery and if the belt is worn, damaged, or not securely in place, you battery may not be charging as it should.) 3. If you still have not rooted out the cause of your problem, you should "jump it" to get the car started again and check for additional problems. First, check the other lights that might be malfunctioning (trunk, glovebox, underhood). If none of these have caused the issue, and the problem recurs, you will need to have the charging system inspected. The cause could be anything from a bad solenoid, to a malfunctining alternator or voltage regulator. Check with your mechanic to determine the cause.