Laptops :: Mpb Is Not Starting

i have a 2007 15" mbp that woke me up this morning trying to boot up. here's the story: last night after watching a couple comedy channel shows, i shutdown my machine and left it plugged in the wall to recharge. it sat atop my dresser, with the lid closed. i awoke to the boot-up chime and a bright light spilling out of the 2 mm screen/body crack. the machine then rapidly shutoff and repeated this two or three more times more without me intervening --it's possessed!! after a couple hours of investigating the problem, i'm now completely lost on what to do. i've read all the apple support pages, and tried all their suggestions including reformatting PRAM and SMC. however, nothing worked.

here are the facts: - when i press the power button without the power cord attached--i.e. using just the battery--the chime sounds, hard disk (i think) makes its typical sound, the screen turns grayish-white....but....then, i hear a zzzzpp sound from the top left of the body (under the left speaker) and the boot up immediately fails.
- here's the kicker--when i press the power button with the power cord attached, and with or without the battery inserted = nothing happens; however, if i detach, then reattach the power cord, my mbp automatically boots as described above without me touching the power button.
- my battery is fully charged
- i've tried another power cord and battery...same pattern as above