>Hello, i need to give the demo of a program i made but i want that after 2 months doesn't work or allow to work, how can i do this?

Here's what I did to give our clients 30-day access to one of our app's modules:

Along the lines of Nadya's suggestion, I had them install a patch file which launched a small executable that created a specific registry key that contained an encrypted date value (current system date). That way, any on-site techies wouldn't immediately be able to figure out what's going on.

In my app, I'm looking for the existence of the key. If it exists, I throw up a message stating how many days are left. If the key doesn't exist, then the user is not allowed in the module - the only way they can get the key created is by launching that small executable I mentioned before.

If the client decides to license the new module, I send them a new patch which no longer looks at the registry for the "time bomb."

Hope that is helpful.

Laterness,
Jon