Outlook Express to Outlook upgrade

I had MS Outlook Express running on my Windows 98 system. It had quite a few user created folders of mine. I installed MS Office 2000. It appears to have dumped all my created folders when it upgraded my Outlook. It did bring in all my Inbox, etc. mail though. I also have Outlook Express running on my Laptop w/XT. I am still running Outlook Express on it (with all my folders intact). I would like to upgrade it to the full version, but maintain all my folders. How can I do this and fix my other one?
Thanks in advance….John