That's odd... I registered, and that was the end of it.
If you're getting a message every time you start up your computer, then it must be in your startup group... you can remove it from there without hurting anything.
I have the same problem with being asked to register when I already did that. I don't understand why the suggestion is to delete the reminder.exe and leave an empty folder that serves no purpose. Why not delete the Register folder and be done with it?