If you followed the steps in my post from August on merging your Outlook and Gmail contacts, you may have ended up with duplicates in your contact lists. Microsoft's advice for deleting duplicate contacts is to sort them by the date modified, Ctrl-select the ones you want to remove, and press delete.
The problem is, the duplicate entries probably aren't identical, so you're almost certain to delete some data along with the dupe. What you need is a way to merge the information in the duplicate contacts. There's no such feature in Outlook, but if you're willing to spend $30, you can make short work of your extraneous Outlook entries by running 4Team's Duplicate Killer for Outlook.
The program deletes or merges duplicate e-mail messages, calendar entries, tasks, and notes in addition to contacts. I tested the program with Outlook 2007 but, according to the vendor, it works with Outlook 2000, XP, and 2003 as well. The new version, 3, is said to work with "Microsoft Exchange type folders including public folders," according to the vendor's Web site, but I ran it on a standalone Outlook installation.
After you install Duplicate Killer, you'll find three new items on Outlook's Actions menu: Duplicate Killer Advanced Wizard, Duplicate Killer Quick Wizard, and Merge. When in your Contacts list, you also have the option to "Search for duplicates in distribution lists."
The Advanced Wizard lets you specify the folders to search for duplicates, the fields to compare, and various actions you can take when duplicates are found. You can also save your selections as a profile and send the profile to an e-mail address.
The Quick Wizard provided all the options I needed without having to work through as many option screens. The current folder is selected by default, as is the option to compare and merge, so you simply click Start and let the program do the work.
The program made quick work of my duplicate Outlook data: the process took about a minute in a list of about 75 contacts, 27 of which were dupes. I didn't notice any missing information in the resulting merged entries. The only downside to Duplicate Killer is that the trial version will merge only five records. That's not sufficient to get a real feel for its capabilities. Still, if you have dozens of duplicate contacts—not to mention e-mails, notes, tasks, and calendar entries—the program can save your hours of manual data entry and cleanup.