Question about Outlook Express

I had to form new email groups when I was switched becaue I couldn't find my old groups in the contacts.  When I send email using the new groups, people that were in the old groups are receiving the email, yet their names are not showing in the new group list.  Where are the old groups?  I've tried deleting some contacts completely, but they're still receiving my emails. Others, I've put in new groups, yet they're still receiving the emails of their old groups.  How can I pull up my old contact list and edit the email groups?