Did you ever go on vacation and have 100's of reminders fire when you return and open Outlook? While it's not a problem with Outlook 2002/2003's unified reminder window where you can select several items to dismiss or dismiss all at once, dismissing reminders one at a time in older versions gets old fast.

Go to Tools, Options, Other tab, Advanced button and remove the check to display the reminder. This has the same effect as dismissing reminders and will affect all past due reminders as well as any that come due while it's disabled.

When you return from vacation, don't forget to turn it back on.

If you forgot to make the change and have 100's of reminders fire, you can turn off reminders, close then reopen Outlook. All past due reminders will be turned off (dismissed) for you when Outlook reopens.