>Is it possible to create database which would be readable only within a my program (some sort of password)? Data are collected with a lot of effort and I don't want someone who has installed VFP (and not purchased program) be able to read and use my data in any other way. My intention is not to encrypt data which whould be decrypted in a fly within a program because of speed.

As Hilmar mentioned that are some products to do this on www.hallogram.com. As a matter of fact, one of them is Cryptor from Xitech. This works really nicely, as it takes only a few lines of code to make the encrypted data available to your program, and has very little hit on performance.