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I dont know if this first step is going to help, but its worth a shothttp://support.apple.com/kb/HT1379
Once you have reset the pram, try to boot into safe mode.. If you cant boot.
Then here is my advice.. Go ahead and format the hard drive. ( yes, this will erase your files)
Once it is formatted , another mac will be able to see it again..
Then, you can run a forensic file recovery program on the drive , and recover probably 80-90 percent of the photos.. ( even after the format and deletion)
The program below, is pretty effective..http://www.wondershare.com/data-recovery-mac/
Im also pretty sure that at this point you realize that at the end of the day, your going to have to reformat and reinstall.. Ive had great luck with file recovery programs..Like I said, you wont get all the pictures back, but you will get a vast majority of them.
if you have any further questions, let me know.
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