I lent an old MBP (15") to a friend. (MBP 3.1) Somehow, she managed to damage / destroy the Magsafe adaptor. I realized I had a cable with a Magsafe adapter still on it from an old 13" MacBook (the power unit packed up - so i nipped the cable off it before chucking it out). I replace the now crushed MagSafe adaptor with the "good" adaptor from the old 13" MacBook's power supply (so now the old MagSafe adapter from the 13" MB is connected to the 85w power supply for the 15" MBP) Green LED comes on - but no power. Remove battery & power - do SMC reset - still just green LED & no power. Remove battery & power, SMC reset again, but this time keep holding the power button down as I connect the MagSafe adapter - continue to hold for a further 5 secs, release power button, & press power button again. Machine starts up. However, the fans are flying at full speed & keyboard backlight does not work. Shutdown, restart & do PRAM reset (3 loops). Machine restarts - fans still at full speed. (all other functions are perfect). Is there an incompatibility issue with the MagSafe adapter that came with the power supply units (60w or something) & the MBP's 85w power supply. I do know the centre pin on the MagSafe adaptor carries certain info between the power supply unit & the machine itself. ***Note*** A friend has the same spec machine as the one in question here, manufactured about 3 months apart. My power supply (with the newly attached magsafe adapter) starts his MBP perfectly. His power supply starts my MBP perfectly (as it usually should). This to me, seems to eliminate a problem on the logic board Any ideas ?