There are a couple of things you could try,
This may sound silly but have u looked in your recycle bin? Also If your folders have somehow been marked as 'hidden' folders, they still exist but will not be visible. Open My Documents and click on Tools then Folder Options. Click on the View tab and under the Advanced Settings list tick 'Show hidden files and folders' and click OK. If that doesn't work for you there are some good recovery programs out there, I've included one which I think is good, it's called Recuva :http://recuva.en.softonic.com/
If all else fails you could do a system restore.
you could use it to go back to the last time you can remember the files/pictures being on your PC.
Start>Programs>Accessories>System Tools>System Restore
I hope this is of some help to you and you get your pic's back!