How is this even possible? Wiped drive but Outlook settings are still there!

We've been having issues with users at our agency corrupting attachments when they send email. After trying everything I could think of, I finally decided to just wipe all the computers (25 in all). It worked on the first 2 computers, but today I did the 3rd and 4th ones, and it doesn't appear to have worked. Aside from that though is the fact that after I reinstalled Outlook 2002 and logged the user back into the domain, her email settings were still there! How is that possible?? I was under the impression that these settings were stored in a registry key.