You can also have the battery tested at most auto stores. It's unusual for a bad battery to keep the car from running after a jump. It's possible, but sometimes the voltage regulator craps out when there's a significant demand for charging current (like right after a jump).
The new battery won't hurt, but if your alternator or regulator is dead the new battery won't get the car too far.
I highly recommend a trickle charger too. Comes in handy keeping weekend cars topped up and also helps when you accidentally kill a battery on occasion ;)
