I have 15" Macbook Pro, which would not boot up. I removed the hard drive and it will boot as external via USB and runs with no issues. When I put it back into the computer it will not boot, the computer can see this hard drive when i hold down the options button, but after picking it i get a kernel panic message to restart the computer (which i never have gotten running as external). I have tried putting in a new hard drive (internal) and running the OSX install disk however before getting to choose where to install to the computer shuts off. If I hold the options button, while booting, the computer does not recognize any drive and only shows me the start up disk. I have read a lot of posts from people who say after replacing the hard drive cable, their similar problems were fixed. Is there any way to know if it is the cable or the logic board? My only hesitation with just replacing the cable is that regardless of which hard drive i have internally, when the computer starts, I can hear the hard drive start and the light activates. If the hard drive is getting power does that mean the cable is fine or would it still be possible to get power, recognize only the original hard drive, and still be a bad cable?