> want include lines of code that will disable my software and delete/destroy the data <

One of the things that works well is to put a "counter" somewhere that when it is hit, the software will inform the user to purchase the package. I have used this sucessfully with full packages that had like a 90 money back guarantee, and after the 90 days I would supply the final key. I normally would put this in a Windows Registry key somewhere that would never be recognized as part of your software, which makes it impossible to trace. Actually, I do it in two places - one which is kind of obviouse and not used, and then the secret one. The person will usually spend forever trying to figure out the obviouse one which actually has no effect.

You could also "encrypt" some of the data itself as its saved, so that you are not destroying the user's data. It's just that its not much value apart from your software un-encryption. Then when the sale is finalized you could have the software un-encrypt this and not use the encrypt feature again. To me, the encryption part is not worth the effort as they would have to convert the data to something else anyway and probably use a lot of its usefulness.

Just some thoughts...

Mel Cummings