Currently Being ModeratedMar 19, 2013 9:17 AM (in response to TheREALCloudPainter)
If you can get to your files, back them up off the machine first to a storage drive (not TimeMachine as it's likely bonked too)
Use the emergency quick copy method
Mountain Lion upgrade doesn't affect your files, if you erased the drive or Macintosh partiton with the 10.6 (without Secure Erase) that might have but OS X writes to the front of the drive and thus your files are still likley on the drive.
If you don't have a backup of your files off the machine, your going to have to go this route first and spend $100 for Data Rescue.
Once the files are recovered, then you can do this if you want to go back to Snow Leopard (and then upgrade to 10.8 or not)
Make sure to select the ENTIRE drive makers name and size to erase the entire disk if going to use the 10.6 install disks.
If you want just to restore Mountain Lion, then do this as there is a Recovery HD partiton on the drive and target the Macinstosh HD partition, you will need your Apple ID and password.
Note that Mountain Lion will NOT run your PPC based software you had under Snow Leopard.