If you never backed up your hard disk and you really can't lose 20 years worth of pictures, then send the disk to a data recovery place like OnTrack. You can try some tools by yourself, but only if you can afford to lose those pictures or they aren't worth the significant cost to recover them. It's unfortunate that so many users assume that hard disks never fail.
Edit: If you really want to perform the recovery by yourself, you could make a complete copy to another disk and then try to recover from the copy.