First, I don’t think you “can” have duplicate accounts. When those accounts were created it would not let you create the duplicate….
There is the Softerra LDAP browser (http://www.ldapbrowser.com/) that will allow you to do query and view Active directory in it’s LDAP form..
I also use vbscripts to get info from AD. There is a fairly simple one that I use to get email addresses. If you would like it, email me directly. You will have to modify it to grab the attributes you want and to authenticate to your domain, but it works for me..