Very seldom do I format cards. I use to use the move option in WindowsXP, which deleted the images from the card, but Vista doesn't have that option, so I use cut and paste which does the same thing.
When you format a card in the camera, all you are doing is deleting the File Allocation Table, called the Fat file for short, and not the image files themselves. This is why file recovery software can recover them, as the images are still there.
You don't have to delete each image, just select the folder they are in and delete that, and all reference to those files will be deleted from the FAT file. Reformatting doesn't harm the card, as all you are doing is clearing the FAT file.