History: I replaced my 160 GB hard drive with a 500 GB in June.
Problem: Cable damage with pictures, source unknown.
One day I open the lid on my MBP and all I have is a black screen and the beach ball. Restart and I intermittently get the the login screen, folder with question, no symbol or just nothing. I get the same result when I swap in an old drive with Snow Leopard. Using an external case I try to boot both hard drives from usb with the same result (I left one of the hard drives connected both times). I'm guessing I have two bad hard drives.
I bring it to the mac store and they tell me its the hard drive because he was able to mount his hard drive onto the system. Granted he didn't tell me he disconnected my hard drive cable in the machine and booted from usb. I get an RMA from the hard drive company and in 3 days I have a new hard drive only 2-3 weeks old. Same result as before!!! Hard drive can't be seen on my MBP or another iMac.
Co-worker hands me his SuperDuper backup and I'm able to boot his hard drive and OS. On a whim I decide to use his usb cable instead of mine. And it worked. Thoroughly perplexed now I realize that if I disconnect my hard drive cable and boot from a working usb cable I can function. Guessing its my hard drive cable or some interface on that path I do a Google search and ifixit shows up with several users reporting the same problems I presented at the start of my adventure.
The moral of the store is that my usb cable and my hard drive cable were both faulty.
At this point I'm a pro at dismantling my MBP. The Guide is helpful if you need it but installation is easy without it.
I couldn't for the life of me get one of the two small screws that hold the cable down. The small screw with loctite like material on it closest to the superdrive slot is now stripped and stuck for eternity.
Disconnect the hard drive cable from the logic board and boot a bootable drive from usb/firewire with a working cable.
If the bootable drive works with the hard drive disconnected your logic board is working.
Check the physical for damage. Look my pictures.
Buy from ifixit, very good experience. Product arrived quickly and when I called customer service for account help they were helpful and knowledgeable.