Hello apple community, I have a 15 inch MacBook Pro 2008, and I decided recently to replace the 250 Gb hard drive with a new WD Black 500 Gb hard drive. I backed up all the data onto my external hard drive and replaced the hard drive. Now I am trying to enter the disk utility to boot from the disk utility by holding the option key. When I turn on the computer and hold the option key it gets stuck on the gray screen. Does anybody have any idea why this is happening? My exact model is "MacBook Pro (15-inch, Mid 2009) and (15-inch, 2.53 GHz, Mid 2009)", according to the technical specifications page.Thanks.