Corrupted Image Files
Corrupted image files thankfully don't happen too often. They can be caused by a number of hardware failures.
These problems are impossible to fix if the issue is with the memory card. If the image on the card is good (viewing it on camera) but corrupted when you transfer it to the computer, it may be that your card reader or cable is at fault.
Once your photo is on the computer and deleted from the card, there is nothing that can be done to correct the problem.
It may be possible to recover a good portion of the photo by cropping - if photo editing software is able to open it.