Here's how I do it!!
If the EXEC file is on a back-up CD or other media, drag it onto your hard drive. If it's on your hard drive already, option-drag to make a copy. Now add the proper suffix to the file if you know it. I often lose Quark documents to the EXEC realm after they've been stored for a long time, so in my case I add .qxp to the end of the name. (Notice how EXEC docs never have the suffix on them? But other files just as old WITH suffixes such as .pdf seem to survive?)
Now, once you've added the suffix to your file and told your Mac that you are sure you wanted to do this, you will probably be able to open them just fine.
If you guess the suffix wrong, I think you can just try again, till you get it right.
I hope this helps everyone.
OH and by the way, if you have folders that you KNOW darn well have files in them, but your Mac says they're empty -- same situation. Drag it onto your hard drive first -- then you'll see it suddenly start copying all those files you were missing. You'll have to do the same for any sub-folders that appear to be "empty" too. Since they're already on your hard drive, just option drag to make a copy first and open the copy to view all your files.