Setting up a trial version on a application

[Warren Kuhl]

I have a trial version of my software which I have limited the
functionality.  I am possibly looking into changing this into a timed
trial version (ie. 15 days).

Are there any good examples of this anywhere?  Trying to figure out
how to store the date the application is installed...without making it
to obvious where the user can just uninstall the application and
re-install to start the trial over again.

Thanks,
Warren