15" Penryn Won't Start Up - Single Beep

My MBP of 2 years has been acting up lately. For the past few weeks I have experienced random shutdowns, and yesterday after closing the computer to sleeep I could not turn it back on. Pressing the power button was accompanied by a medium-volume beep coming from under the left speaker area.

Each time I attempt to boot, I hear the hard drive turn on and there is a whirring noise, shortly followed by a beep which shuts everything back off. I just attempted to switch my two RAM sticks and reseat them, but still no start up. Is this a more serious problem? Any help would be greatly appreciated.