>We want to create a executable program which is either registered or unregistered. When unregistered we want to install an expire date which tells the user for how long he/she can use the program unregistered. However when the user decides to register the program we want to give the user some sort of code to install so that the program recognizes that the program is registered.
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>Does anyone have a clue or different kind of solution for this problem?
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>Thanks in advance.

The first time the user runs the application, encrypt the DATE() and store it in the registry. Then, check it each time the application is run. When they enter the code, store that code in the registry. If the code exists, then it is a registered version.

There is another way to create a demo version. You can limit the number of records that can be added. I've used this successfully. There is information on my web site on how to do this.