Photoshop .psd files converted to Unix Executable files

Question

I'm an illustrator and I store my art on CDs and DVDs. After a period of time my files are converted from Photoshop .psd files to Unix Executable files and I can't open them. What can I do to get my work back??? -and keep this from happening in the future. Why does it do this????
Thanks for any help.

Answer 1

The file sizes range from 22.2 MB to 67.9 MB.
Size isn't the issue then. Linc was asking that question because we see that with other file types. Older fonts in particular, which have all of their data in the resource fork. If that gets stripped, you end up with a zero byte file.
Does that mean I'll have to go through the Adobe authorization process for Photoshop again?
If the version of Photoshop you're currently using is already activated, then no. Either way, it has nothing to do with .psd files showing as UNIX executables.
In Windows, any file that doesn't have an association to a program is displayed as a white, dog-eared piece of paper with the Windows logo in the middle. That's Windows' way of saying, "I have no idea what this is." In OS X, (except for those files which actually are UNIX executables), displaying them as such is OS X's way of saying the same thing.
I thought I was home free when the icon changed to a thumbnail picture of the illustration, but PS refuses to open it saying it is not a Photoshop file. ???
Now that is weird. As of Snow Leopard, Apple put the old Type and Creator codes to rest. It will read them as a last resort to try and identify an older file, but none of Apple's applications add them to any file they save. For better compatibility with Windows, and OS X's own underlying UNIX core, file extensions have taken their place. So adding a .psd extension should have worked. Without playing with one of your files, I couldn't tell you why Photoshop declared it wasn't a valid .psd image.
On a side note, Apple added Uniform Type Identifiers to OS X to keep things separate. A big problem in Windows is that multiple apps may use the same file extension. EPS is a big one in printing. So you have Photoshop, Illustrator, Freehand, Quark and others all using .eps for Encapsulated PostScript files. However, Windows can only associate one application to any given extension. So if Illustrator happens to be the one tagged to .eps files, it will try to open any file ending in .eps, no matter what program actually created it. OS X keeps them separate with Uniform Type Identifiers. So even though multiple files may have .eps file extensions, the extra metadata keeps track of what program it actually belongs to.
This is what is part of the LaunchServices database, and was why it was my first suggestion. If that database is wonky, you'll see weird things like this. Have you tried clearing it yet?
The files are fine when newly burned to CD. It is only months, or years, later that they become Unix Executable Files.  This has happened to just about all of my CD backups and it's frustrating to think that CD backup doesn't work across newer OSs and Photoshop upgrades. I suspect that may be the problem, but it just shouldn't happen.
That shouldn't make a difference. I've got a bunch of very old files created in Photoshop back from OS 8 on CD. No file extensions, as nothing did at the time. Just Type and Creator codes. They all open fine in PS CS5.5 in Snow Leopard, though the native Photoshop files do need to have a .psd extension added.