Outllook 98 and Win2K Conflicts

We have several Dell Inspiron 4000 notbooks running Win2K and Outlook 98. Every time a normal user launches Outlook, they are asked if Outlook is to be the default manager. Despite saying Yes, this messgae keeps appearing. I believe there are user restrictions in the registry when Office 97 suite etc is on Win2k. What is the registry key that needs to have increased user rights?