My MacBook Pro 2009 model turns on but all I see is the apple icon and a loading bar

Applelover162000,

boot your MacBook Pro into Recovery mode by holding down a Command key and the R key as it starts up. Once the Mac OS X Utilities menu appears, select Disk Utility. On the left-hand side of the Disk Utility window, select your internal disk’s boot partition (typically called “Macintosh HD”). On the right-hand side, press the Verify Disk button if it’s not greyed out; if it is greyed out, or if it reports that errors were found, press the Repair Disk button. Once the verification/repair is completed, exit Disk Utility and select Restart from the Apple menu to restart in normal mode. Are you now able to get past the Apple logo and progress bar?

Applelover162000,

if the problem is unrepairable, then you’ll need to completely erase your internal disk, reïnstall the version of OS X that’s on your grey Mac OS X Install DVD, and run Software Update to get it up to date in that version. If that takes you to Snow Leopard 10.6.8, then you can redownload and reïnstall Mavericks. If that doesn’t take you to Snow Leopard 10.6.8, then you’ll need to reïnstall Snow Leopard from the white retail DVD and run Software Update to get you to 10.6.8, at which point Mavericks can be redownloaded and reïnstalled. Once you’ve run Software Update from Mavericks, you can restore from your internal disk’s latest backup..

If you don’t have a backup of your internal disk, and you’d like to try to save any files on it, there are two ways to try making one at this point: one is by booting from an external bootable disk, and the other is by starting your MacBook Pro in Target Disk mode so that another Mac can treat your MacBook Pro as an external disk. In either case, you’ll need to copy whatever files are salvageable from your internal disk to the system which you’re booting from. Once you’ve got Mavericks reïnstalled, I’d highly recommend purchasing an external disk to use as a Time Machine backup destination.