I have a macbook pro 17' and I just replaced the hard drive with a seagate 500GB 7200 RPM. I cannot seem to boot from this disk at all. I've restored, reinstalled the OS, but still nothing, every time i go to start my computer I get the error, "please shut down your computer and restart" and when I do that, it 's the same problem. I have to restart with my old drive and I can see the new HD and use it's application without any problems, I've done disk repair, disk erase. everything seems to be fine. but why can't it use my new HD as the startup? what piece am I missing?