>Craig,
>
>Alex Feldstein recommended me to use your VFPEncryption.FLL for encryption/decryption. I download the zip and read the documentation. It works great! However, I do have one question. When I decrypt it with the wrong key, the function doesn't throw any exception or SetLastError, how do I determine whether a wrong key is entered? In other words, how do I know it decrypted correctly?

Just an idea: why don't you also store a known string, and decrypt it? If it doesn't match the expected string, the key is wrong. You could use something that won't change, like your name, or name of the exe.