Folder with a question mark

If you see a folder with a question mark appear instead of the Apple logo, it means your Mac couldn't find a local or network-based startup disk. This can happen if the disk selected in the Startup Disk pane of System Preferences isn't available. Wait a few seconds to see if your Mac is able to locate the startup disk you specified.
If you still see a question mark after waiting a few moments, use Startup Manager to start up your Mac, then re-select your startup disk from System Preferences.
If a question mark appears after you install a software update, re-select your startup disk using OS X Recovery.
About the screens you see when your Mac starts up - Apple Support
You Mac may or may not have internet Recovery,
Computers that can be upgraded to use OS X Internet Recovery - Apple Support
Since you do not have backup,
- Get an external USB drive and format it in OSX extended
- try booting to Recovery
OS X: About OS X Recovery - Apple Support
and then try either cloning the internal drive to the external drive by:
http://www.newertech.com/tech_support/manuals/mac/clon_data.php
or using terminal in Recovery to copy individual files and folders
1. Copying Files to External Hard Drive via Terminal When booted to Recovery?
If you can't boot to Recovery then boot form Snow Leopard install DVD and try the cloning/copying.
Then:
- Try resetting the SMC and NVRAM/PRAM
Intel-based Macs: Resetting the System Management Controller (SMC)
About NVRAM and PRAM
- Try starting in Safe Mode
OS X: What is Safe Boot, Safe Mode?
- Boot to Recovery and repair the startup disk
OS X: About OS X Recovery - Apple Support
- If it is repairable reinstall the OSX
How to reinstall OS X on your Mac - Apple Support
- If you do not have a backup use disk utility to restore the internal disk to an external disk so you can try to recover data.
Then format the startup disk and do a fresh install of OSX
If the HD is not repairing then likely the HD has to be replaced. If you replace it I would install an SSD instead.