I wrote a utility for photographers that I plan to sell online pretty cheap ($10). I'd like to allow the user to try the software out for a week or so before asking for a license. Since this is a personal project and the software is not very expensive, I don't think that purchasing the services of professional licensing providers would be worth it and I'm rolling my own.

Currently, the application checks for a registry key that contains an encrypted string that either specifies when the trial expires or that they have a valid license. If the key is not present, a trial period key is created.

**So all you would need to do to get another week for free is delete the registry key.** I don't think many users would do that, especially when the app is only $10, but I'm curious if there's a better way to do this that is not onerous to the legitimate user. I write web apps normally and haven't dealt with this stuff before.

The app is in .NET 2.0, if that matters.