The reminder program is something I wrote on a whim, in a spare ten minutes. It really is very simple, but could be rather useful. The idea is, that when your system boots up, Reminder is run and looks at the system date, and prints a message if its going to be someone's birthday next week, or if you have a dentist appointment that day. The dates and messages are stored in a text file (an example is here), and the program is run from your autoexec.bat file.
Why not download the small (11K) file, REMIND.ZIP. The file includes the documentation and an example REMIND.INI file.