Luckily, photos and images are easier to recover than most other data on a hard drive... If they have already been overwritten, you will be told which ones are perhaps usable and which are not.
Just do NOTHING else with that hard drive until you have run recovery software...
Install Windows on a new drive, then put your old "wiped" drive in an external enclosure connected to the main computer with a USB or Firewire Cable... then run the recovery program.
This way, no more space will be overwritten, and any recovered files will be copied to the newly installed Windows Driver for copying to a CD or DVD.
It takes some time, but works well.
Most recovery programs will have to make up a new name for the image, as the first letter has been wiped in the "erasure" of the file... But you can rename them back to usable names after you complete the recovery.