Moved to Photoshop forum.
Welcome to the forum.
What are "PDD images," and how did you convert them to JPEG?
Do those JPEG files Open in other programs, like IrfanView, or another file viewer?
Do you have Photoshop CS 3, or other version, installed?
Do you get an error message, when you try to Open those JPEG images?
I think PDD was the old PhotoshoDeluxe format.
Are you seeing a message in the images that says "This layered image was saved without a preview, you need Photoshop 3 or later to open this file"? If so, the JPEGs are worthless, and you need to recovert the PDD files so that their layers are preserved.