>How do I do an upgrade to an existing application once its has been installed and data has already been entered into the database? I have used the standard FoxPro installation disk creation program.

You either need to write code that can check the existing data structures and use ALTER TABLE commands, for example, make necessary changes. This is non-trivial. There's a lot of protection you'll need to write to make sure a mid-process crash doesn't corrupt the database, for example.

Another choice is to use StoneField toolkit, which will help you manage this for you. www.stonefield.com.