Click the Calendar tab on the left side of the Outlook Options Window.You can change the default settings in Outlook so that no default reminder is set or to change the default time for reminders. Outlook automatically sets reminders for new appointments you create. '15 minutes' will display a reminder 15 minutes before the appointment begins.) Select 'None' if you do not want a reminder for this appointment. In the 'Options' group in the ribbon, locate the 'Reminder' drop-down box and select the time you want the reminder to display (i.e.Double-click on the desired appointment.
For information on changing the settings for desktop notifications, see the Desktop Alerts help page. Reminders are not the same as desktop alerts, which appear when you receive a new email.
