I've got a Macbook Pro Early 2008/A1260/15". It's a 2.5Ghz running 10.5.8 with 2GB of RAM. Model Identifier MacBookPro4,1, Boot ROM MBP41.00C1.B00 and SMC version 1.27f2. Sometimes it will not boot. When it does not boot, the only thing that occurs when the power button is pressed is that the hard drive spins up. Nothing else happens. The display does not turn on, the system makes no sounds, the light on the latch does not illuminate, and the fans do not activate (I have tried booting with the case open to watch the fans and they do not spin). If the AC adapter is plugged in during such an attempt, the hard drive seems to stay on indefinitely, until the power button is held down for 5 seconds. If the laptop has only battery power during such an attempt, the hard drive will power down after a couple of seconds. There are 3 sorts of things that seem to allow it to boot in such a scenario: 1) Time. If I wait for an hour or sometimes many hours, it boots fine. 2) SMC reset. Sometimes disconnecting AC and battery and holding the power button for 5 seconds, then reconnecting power allows a successful boot 3) Random repeated attempts (generally with AC power) of holding down power to shut down the drive after an unsuccessful boot and then trying again. This sometimes works. At other times, it boots fine and will boot fine repeatedly. I tried running Apple Hardware Test. The short test was successful. The extended test was also successful, although during the test the mouse froze, and after the test succeeded, the mouse remained frozen. I have tried re-seating the RAM, swapping the RAM sticks, trying each of the 2 RAM sticks individually in each of the 2 slots, but none of this helps. I have removed the hard drive and attached it to another computer where I ran a SMART short and extended self test, both of which were successful. There is no evidence that there is anything wrong with the drive. Any ideas? Is it more likely to be the "logic board" or the so-called "magsafe/left I/O board"? Please help. thanks.