You can delete an appointment or task from the Calendar and Task Sheet. If you want to complete a task and therefore delete it from the Task Sheet, see Completing a Task.
To delete an appointment
Right-click over the appointment you want to delete and click Delete Entry.
When prompted, click OK to confirm the delete.
To delete a task
Click on the task in your task sheet that you want to delete.
In the window that appears, click Delete. When prompted, click OK to confirm the delete.