Method for providing a trail period on a program

[Josiah Carlson]

> I'm searching for a good way to provide a "trail
> period" (something like 90 days) for a commercial
> application that I'm writing.  I'd like something
> that can easily stop working 90 days after
> installation.  Can anyone point me to something
> that exists already?

Using windows registry pseudo-code

if stoptime_not_in_registry:
     stoptime = time.time() + 90*24*3600
     store_stoptime_in_registry(stoptime)
if time.time() < stoptime:
     continue working
else:
     give registration warning and quit


FYI: most (if not all) methods for restricting users to some limited 
trial period are flawed in some major way; users can take a snapshot of 
their machine before installation and after installation and single run, 
and determine what has changed to determine exactly what is necessary to 
remove such protections.

  - Josiah