How can I fix a JPG file?

I have some photos taken with my Sharp videocam a year ago. After I have saved the photos on CDs, I still could retreive the photos at that time. However, I could not get it done recently. When I retrieved it from the CD, I was notified that the files have unrecoverable errors. Thought I have tried it with other programmes, such as photoimpact or ACDSEE, I still could not get it through.