DayMate is an excellent day planner that helps you get organized in both your business and personal life.
It enables you to create reminders for any kind of event: anniversaries, meetings, personal dates and so on, including system tasks like turning the PC off or launching a given application. Each reminder has its own color code and can be set to warn you with a pop-up window, a sound or even by sending you an e-mail message.
If you have ever used Microsoft Outlook, you'll have noticed that DayMate's interface is very similar to Outlook's calendar. In any case, you'll find it extremely easy to use. The only thing I missed is the possibility to create new categories for events but, otherwise, DayMate may the planner you're looking for.