Here is an excellent way to delete duplicate contacts in Micrsoft Outlook. I always add contacts even though they already exist in there and this little trick is very handy. Also Synching with different devices also wrecks havoc on my contacts

1. Go to Contacts.

2. Click View, mouseover Current View and select Phone List. This will create a list of all of your contacts in a column based view.



3. Right-click a column header and select Field Chooser from the resulting menu.



4. In the Field Chooser box, use the dropdown and select All Contact fields.



5. Select Created.



6. Drag Created to the Colun Headers to add it to the list. Close the Field Chooser box.



7. Now click on the newly added column header (Created). This will sort all of your items by the date that they were added to your Contacts.

8. Scroll down to the first contact in the list that is to be deleted and select it.

9. Scroll down to the last contact that is to be deleted. Hold down the Shift key and select this contact. This will highlight all of the contacts that you are going to remove.

10. Press the Delete key. The duplicate contacts will be removed.

11. Click View, mouseover Current View and select the view you normally use for your contacts (such as Business Cards).

12. Your Contacts should not display any duplicates.

Thanks to Tech Recipies