I have a 17" 2009 Macbook Pro that is very frustrating. It starts everytime you press the power button, however only say one out of 100 times will complete booting. It will just shut down usually just after the desktop loads, but sometimes before. If you wait long enough eventually it will fully boot and you can use it like normal for as long as you like, days, weeks etc. Can play games, watch movies, surf the internet whatever everything working perfectly. But if you shut if off for any reason, you have to deal with this all over again. I've tried, a new hardrive, new memory, and all of the hot keys resetting shortcuts. I'm starting to think it's some sort of board level issue and I'm wondering if anyone has any ideas on where I should look. SMC maybe?