This is the worst and most mystifying problem I've yet run into with my MacBook. It's from late 2006, but the RAM (3GB) and HD (Western Digital 595GB) are not original. That said, I'm confident neither of these are the cause, as I've had 'em installed for 2 years and 4 months, respectively. The problem: I press the power button. Computer makes the starting sound. Fan whirs on. Grayish-blue screen with Apple logo. Spinning tick wheel underneath. You know the drill. But then, it just suddenly and inexplicably turns off. Fan off, black screen, no HD activity. Nothing. Aaand repeat...nothing seems to change. This started 10 minutes ago. I'm on a friend's computer now, since I'm at college - this also means that I do not have my installation DVD or indeed any of my wide array of computer-fixing tech components save for my mini screwdriver set. Since I know it's gonna come up - The last thing I did on the computer was shut it down while it installed the latest update for Safari (which I don't use). Seemed everything was going okay - it turned off and I left for dinner, came back all set to write an essay and the darn thing won't make it to the login screen. So naturally, there are no error messages or anything like that. No weird beeps or noises from the HD or elsewhere. Frankly, I'm just plain mystified. System specs (in case it's relevant): MacBook (black) 13" late 2006 3GB DDR2 SDRAM 640 GB (595GB) hard drive 64MB Intel GMA 950 graphics Mac OS X 10.5.8 Leopard - I do not own the installation DVD, I got it from my school (and I don't go there anymore). Nothing out of the ordinary as far as recent hardware or software changes are concerned. I've ruled out the battery as a problem as well, since it is at 92% of its original capacity (how, I don't know) and the computer does the same start-up-then-shut-down routine whether the battery is in or out. Please help if you can. Even if you just post guesses as to what's wrong, that might help. As I said, I'm a college student. I have a LOT of technical knowledge and will understand whatever jargon you throw at me, but I don't have tools or resources readily available. I am in central Pennsylvania and the closest Apple store is actually quite far - closer to my home, and I may make the trek back if at all necessary or possible. If I don't immediately respond, it's because I'm not at this computer all the time, but rest assured I'll continue to check this thread as much as I can. Thanks in advance for any and all help!