Import/Export Distribution Lists-Outlook

Users in my office use Outlook 2002 and 2000. Users create groups (distributions lists), and often use Import/Export to back up the address book. However, when importing the contacts folder, the groups are not imported at all. If I have to installOutlook to a new computer, I have to recreate all of the groups because I can't get the distribution lists from the file I've exported. How can the groups be saved, and imported when needed?