Controlling who can run an executable

[Istvan Albert]

>was using to track clients and transactions.  He couldn't demonstrate
>the program for one reason or another because it was protected in a way
>that neither could circumvent. (She didn't remember how it was
>protected, she had hired this person a long time ago.)

I'd venture to guess that neither of the people above knew much about
programming. So do the same, create a security measure that protects
against this level of 'threat'.

As others have pointed out the simplest way would be to detect the
presence of a hidden file, or some hardcoded system value, mac address
etc. Obscure this step even more by encrypting some of the information
so that one can't just simply view it in a hex editor.

Istvan.