W10

I have files of various formats (pdf, ppt, doc, etc) that won't open because they're "...unsupported file type or have been damaged". I don't know why they're damaged....they were all originally on other computers (which I don't have any more) so possibly in the process of backing up. I'm on W10 now but the original computers were W7 & some might've been from XP machines, I don't remember for sure (some of the files are nearly 20 years old).

I've tried free applications like Piriform's Recuva but had no success. So, what applications would people recommend, please?

Also, does it matter that they've been transferred from ONE PC to another....will that effect the chance of successfully recovering/repairing them?

ThanksIf the files are showing with file names and extensions, DATA RECOVERY software will not help.
Do any of the files from the old computers open ?
If there is a PDF which opens and one which doesn't when you do properties on the files are the they same ? Are the files which don't open kilobytes in size instead of megabytes as an example?
If they are only Kilobytes it is unlikely they copied. Only a short cut to the file or the file name. In which cause the file contents wasn't copied and nothing now can be done.

There is a recovery program which would give a lot more information on the files called Reclaime https://www.reclaime.com/
When it does a deep scan of the drive it has a viewer for most file types and if it can't display the file it will show the Hex data which you may be able to use to repair the files.
There is online file repair tools if you google PDF repair , doc repair which maybe worth trying.
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Do any of the files from the old computers open?

Are the files which don't open kilobytes in size instead of megabytes as an example?
If they are only Kilobytes it is unlikely they copied. Only a short cut to the file or the file name. In which cause the file contents wasn't copied and nothing now can be done.