Before you toss the battery, turn the key to "Run" and manually jump the positive terminal of the battery to the positive terminal of the starter motor.
If the engine turns over, the battery is good and you have some kind of solenoid/electrical wiring problem.
If the starter spins and you get slight lunge and then it freezes when the starter gear engages the engine you have a good battery and starter, but a frozen engine (unlikely, IMO).
If the starter doesn't twitch, it's a bad/weak battery, or a bad starter. Hit the starter with the battery charger just to see what happens, that'll narrow it down further.
Should take no more than 5 minutes to get closer to a root cause.
__________________
[insert witty phrase here]
|