Alright guys, this might sound weird and yes, it makes no sense at all, but I've tested it out at least 20 times and it really is the screws that somehow cause the problem: I have a mid-2009 15" MB Pro. I recently had to install a new hard drive, since the old one was about to die. I installed a 750 GB Seagate (basically the same thing as the old 7200 rpm 500 GB 16 MB cache one, only with more capacity). The problem I'm having is very weird and I can't find the solution: When I installed the HDD, secured it with the little plastic bridge with 2 screws and then put the bottom case on with the 10 little screws, it first worked no problem, but after a few minutes, kernel panics started to occur. Every 5-10 minutes, OS X freezes (beach ball) for about 20 seconds and then, either starts working again or I get the dark screen that says I need to turn it off and then turn it back on again. For some reason, when I was testing the hard drive in an external case and then I put it back, without screws first, so that it would be faster to take it out, the system worked flawlessly for hours. Then I decided to screw the HDD and the bottom case back in and guess what, kernel panics again. Do you think this might have something to do with a screw or the bottom case touching some part of the logic board or so? If so, what do you think is the solution? I know you might think it just randomly sometimes works and the screws have no effect but trust me, I've been testing it for 2 weeks now, putting the screws in and then taking them out again.