Help! iMac hard drive failure No Backups

Question

I bought iMac in 2011 and worked perfectly fine until 4 days ago. The first sign was everything became so slow. Every task took about 2 minutes to finish or the mouse cursor spinning forever. Then I started reboosting the system. The problem remained. The following day, I tried to turn on the iMac. However, within 10 seconds, it shut itself down. I tried reboosting on and off for a few more times. Exactly the same thing happend. I haven't done anything to iMac. I mainly use it for surfing on Internet, listening to itune or using iphotos.
Then I realized, since I bought iMac, I never used time machine or external drive to set up the backup files. I was stupifiied that I never thought about it because I secretely believed that iMac will never have hard drive problem on me. I never even had such problems in all my precious PCs. All my files from my previous PCs are in iMac as well as saved word documents, photos, and videos. It would be the worst thing in my life if I lose all of these files including files that have sentimental values.
I already made appointment with apple store genius bar. But while anxiously waiting for the appointment, I wonder if anyone could tell me a solution to recover all my files in iMac.
Thank you!

Answer 1

This depends entirely on the nature of the failure or if there even has been a disk failure as opposed to a system failure.
You might try reinstalling Snow Leopard:
Reinstall OS X without erasing the drive
1. Repair the Hard Drive and Permissions
Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.
If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.
2. Reinstall Snow Leopard
If the drive is OK then quit DU and return to the installer.  Proceed with reinstalling OS X.  Note that the Snow Leopard installer will not erase your drive or disturb your files.  After installing a fresh copy of OS X the installer will move your Home folder, third-party applications, support items, and network preferences into the newly installed system.
Download and install Mac OS X 10.6.8 Update Combo v1.1.
If the above is not possible:
General File Recovery
If you stop using the drive it's possible to recover deleted files that have not been overwritten by using recovery software such as Data Rescue II, File Salvage or TechTool Pro.  Each of the preceding come on bootable CDs to enable usage without risk of writing more data to the hard drive.  Two free alternatives are Disk Drill and TestDisk.  Look for them and demos at MacUpdate or CNET Downloads.
The longer the hard drive remains in use and data are written to it, the greater the risk your deleted files will be overwritten.
Also visit The XLab FAQs and read the FAQ on Data Recovery.
If the above is not possible, then you would need to send the drive to a disk recovery service such as Data Recovery by DriveSavers | All Drives, RAID, SSD & iPhones. These services are very expensive and provide no guarantee of success.