PopUp Reminders won't go away even after dismissed and completed

To resolve the issue of reminder pop ups keep coming back once it is dismissed, follow few of the steps mentioned below:

 
Step 1:

Start Outlook using the switch command and check how reminders work. To do that, close Outlook. Go to Start, click on All Programs and Accessories and then Run. In the Run open box, type in ‘Outlook /cleanreminders’ and hit ok. (Note: There is a space between Outlook and /).

Step 2:

You may also scan and repair the Outlook data file and then verify the results:
http://support.microsoft.com/kb/272227

Step 3:

If issue persists, create a new profile and then create test appointments and check how the reminders work.
http://support.microsoft.com/kb/829918