My 13" 2010 MacBook pro will not start. When starting the apple logo comes up and the whirly, and it just sits. It will start in Hardware Test mode and tests are OK. I reset the PRAM and NVRAM. It will not start in safe mode and it will not boot from the Apple disk in the drive. It will start up in Startup Manager, but just shows the hard drive as the only available option. When selected, it goes back to square one. The hard rive is under warranty, but before replacing it, I would like to have the option to erase it and reinstall a backup to ensure it is a hardware problem and not a software problem. What to do now? I'm out of ideas. Please help!