Don't click on "Initialize." For one reason or another your Master Directory Block (MDB) or another component of the hard drive's directory has become corrupted. This can be caused by powering off or disconnecting the drive before you have unmounted the drive or powered down the computer. You must always unmount the drive or power down your Mac before disconnecting or powering off a hard drive. The way to get your data back varies: 1 - If you have your data backed up (at this point you realize the need for back up) you can format the drive and restore your data. 2 - If some or all of the data is not backed up, you can use a disk utility program to rebuild or fix the MDB. Apple supplies Disk First Aid in your Utilities folder for just such disasters or you can use more powerful third party software. Disc Warrior Tech Tool Pro Norton Disc Doctor 3 - Call data recovery and have the professionals handle the details (comes complete with a professional bill).