Won't start. I recorded a video of what it sounds like. Would you suspect a bad battery first or alternator or what? Battery was replaced in August of 2011 (Interstate MT51). Drove car for an hour and 15 minutes 4 days earlier. Car sat for only 2 days. Was working fine until tonight.
And is it safe to test the battery with a Radio Shack voltometer? @ 20V DCV?

 

It does appear that the battery is flat. But that could be because the alternator is not charging it, or that something ran it down.

See if it responds to a jump-start. Once started, let the engine idle with everything else off. Measure voltage at battery, it should be more than 13.5 volts. If the voltage is in the 12s, the charging system is not working.

 

Replaced the battery. It started right up. Time will tell if the alternator is charging it.