Well, after hesitating for months to purchase a replacement battery for my mid-2009 macbook pro, and after at genius bar i have been told that my mac is now considered as vintage therefore they can't officialy replace the battery. i pulled the trigger and purchased a Floueron-branded replacement battery on Ebay.
Just after the operation, to my surprise, my mac didn't turn on. Even though i put the original battery back and tried all the solutions possible (trying to turn on without a battery on, smc resets, checking the ram etc.) my mac now doesn't show any sign of life and apparently the logic board is dead.
i'm suspecting that the new battery caused a short circuit and killed my beloved macbook pro's the logic board.
even though there is no way to be sure that the replacement battery caused the damage, my advise to anyone looking to replace the battery themselves to be careful with those third party batteries on ebay.
unfortunately my lesson was rather an expensive one!
Hmmm. Is there a I/O board on it?