Go into Outlook and press on the Contacts button. You can open each Contact individually and see the category of each Contact. A Contact that came from Orion will say Orion Contact-Sync or something similar. A faster way though is to change your view to List. There should be a column called Category. It could be to the far right, so drag the column header to the left and put it next to File As. You now should be able to clean up the Contacts by selecting multiple Contacts and pressing delete to delete them.
