>I know it's possible to get the hard disk number from VFP. This could be a good information to limit access to an application.
>
>Beside the hard disk identification what could be other things that could be tested to make that copy protection more effective?
>
>Please provide sample source code to do those additional checkings.

MAC Address of the computer's network card. See UT Downloads or search here for sample code. It is very easy to get.