It's no problem at all to get them back. Please see this post for several free software that you can download. You'll need to use a card reader with these programs though:
Recovery Software Links
CR, January 2008
Your camera may have come with un-delete software, or it may be downloadable from the makers website. If you haven't used that memory stick you may be able to run the software from your computer (with your memory stick or camera pluged in) and retrieve the deleted images.
Robbie, January 2008
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I can answer this question...
I deleted some photos from my digital camera accidentliy,how can i retrieve?
