Cannot open files from data DVD - invalid file type error

steveandel

I have a data DVD which I need to retrieve some files from. When I put it in my DVD drive, autoplay runs fine and the file structure shows up fine. There is a mixture of Autocad drawings, Word documents, pdf's and jpeg's.
None of the files will open. The Autocad and Adobe files give 'invalid file type' errors, the Word documents come out as gobbledegook and the jpegs just show that little red cross.
The same happens even if I copy the files from the DVD to my hard drive first and then open them.
Does anybody have any idea if/how I can recover files from this seemigly corrupt disc?
Thanks

Cat695

did the files actually copy and not just the shortcuts?

what size is each file?

steveandel

Yes all the files are on the disc. The disc contains a total over just over 3Gb of data so it is all actually on there. Files vary in size from a few kb to a few Mb.
When copying files from the disc to my hard drive the file on my hard drive is the same size as the file on the disc.