I would like to include some type of copy protection scheme on my applications that would make a retail registered version of my software revert back to a trial version of my software if/when it gets installed on another computer.
In the old days I would simply store all the user information in a record that I tacked on to the end of the exe file. During the registration process I would simply poke those values into the data record on the end of the exe file. This worked great until good ol Norton started flagging my product as a virus because the exe file changed.
I stopped doing that a long time ago. I'm getting ready to create an updated version of my software and I'd like to know how you have accomplshed this.
The information that makes it a retail version should be stored on the target computer, not with the original program. That way, when they try to move the program, it reverts to the trial version because the retail information is missing on the new computer.
The retail information is added via a registration process, using a unique key. There are a number of ways to make this key work only once. One way is to transmit it directly to the program over the internet, where the user never sees it, so they can't manually transfer it to the new computer.