OK, here is the latest. I hooked up a portable battery, one of those battery backup system that you hook to the wall out let at home then use it to start the car in emergency. The car starts right up. This little portable battery looks like this one here (except its red): http://images.amazon.com/images/P/B00030BFJW.01._SCLZZZZZZZ_.jpg

Anyway, the car runs, but if I remove this device the car stops. So then I just let it stayed hooked-up and let the car runs. The car runs for a little while and then it just died, again. The portable battery is drained and I have to take it back inside the home to recharge it. Then tried it again, the car starts, drains the portable battery, same thing.

Looks like I have a dead car battery right, thing is I replaced only a year or so ago and never abused it, ie. never it it run out of juice?

Or is it the alternator after all? How can I check the alternator? I have a voltmeter. Suppose I get it started again next time with the portable battery pack. How can I use a voltmeter to check the alternator?