Don't use that hard disk right now. Anything you do can overwrite them. I'm typing an edit to help you recover them, but that could take 10-15 minutes.
What OS are you using? XP? vista? Win7?
EDIT : okay. So ...
It shouldn't be that hard if you follow this step by step. When in doubt, PM me your Skype address. I can walk you through it.
First thing to do is get recovery software. I'm a big fan of Piriform's Recuva, so I'll use that for this tutorial.
Go to THIS PAGE
and download the Portable version (the middle one). Download it TO ANOTHER HARD DISK OR A USB STICK
, but not to the disk that your photos were on.
Extract the zip. In the Recuva folder (rcsetup143 for the current version) you'll find 2 applications : Recuva and Recuva64. The regular one is for 32bit systems, the 64 one for 64bit systems.
Open the one that suits your PC best. When in doubt, open the regular one ("Recuva").
Once it starts, you can select what kind of files you wish to recover. (pictures, music, etc). Select pictures.
Next it'll ask where. If you use the regular "Pictures" folder or anywhere in "My Documents", click the "My Documents" option.
Otherwise choose the bottom option and select the appropriate hard disk.
On the next screen, Recuva will ask if you want to do a deep scan. You don't have to use the Deepscan option, but chances are you won't find too many pictures.
If you find them, go to the 2nd to last part. If not, close Recuva, launch it again and repeat the whole thing with Deepscan enabled.
Mind you, depending on the size of your hard drive it could take hours to do a deep scan.
The last bit will be less specific because I haven't had to recover files in a while, and certainly not with the current version of Recuva.
Once it's done with the scan, you should see thumbnails. Select the ones you want to recover, and let Recuva save them TO A DIFFERENT DISK OR USB STICK
(sorry for the caps, but I can't stress that enough. If you don't do that, you may overwrite several pictures with the recovered ones)
Once that's done, you should have them back.
Browse through the pictures one by one, to ensure that they are ok. Sometimes a file can be partly overwritten, resulting in a corrupted picture, or one that won't open. Those will be lost forever.