If the disk drive has failed, then you will need a trip to the Genius Bar. To book appointments with the Genius Bar online, please visit this link. However, before deciding to go with the Genius Bar, we have listed some methods that may help you if the issue is not disk failure. If the disk has failed, then the only option would be to replace the disk and recover your data to the new disk from the Time Capsule or any other backup device you may have been using. If you were not backing up, then it might be possible to recover the data by finding a recovery company that can be searched on Google.
1. Disconnect the network cables and the peripheral devices.
2. Give the system a safe boot
Shut down your system. If you are unable to shut down your Mac the normal way, then hold down your system’s power button for a few seconds until it shuts down.
3. Reset the PRAM/NVRAM.
4. Start the system using the Mac OS X installation disc.
5. Remove any third-party RAM
