I just picked up a 500gb samsung HD to replace my stock 100gb drive. I installed the new drive & OSX but when it tries to start up there is only a black folder with a question mark. I've tried reformatting and reinstalling about 3 times with no luck. The computer works fine when I reinstall the old 100gb HD. The 500gb drive seems to work fine as an external, but will not boot OSX! Do the core duos have an issue with large drives? Do I have a software or hardware problem? Thanks!!!