>Yes. And the mechanics of it seem to work fine. Using a hex editor you can modify them manually or use low-level functions. To summarize, the problems are:
>
>1) If anyone ever changes the structure, the header is overwritten and the key disappears. (In my application, this may kill my idea). INDEX, REINDEX, PACK does not effect the key.

If they can change the structure or change the filename, they can ruin ANY solution you come up with. You don't have a technical problem. You have a procedural or policy problem, and I don't think you will solve this one without policy changes.

>2) Header formats change. If DBF header changes in a future release of VFP, this method must be modified to account for the new version.

You're probably pretty safe here. Extremely low probability of changes in all of those bytes.

>3) If someone copies the file via explorer, both files will use the same key (no longer unique), and the 'history' of one of the file will be inaccurate.

There is NO solution that will solve that one, so it's not an issue that would prevent you using the header solution.