Need to change NT & Exchange Licenses

Hi, By mistake we installed NT 4.0 & Exchange 5.5 Servers using our MSDN CDs. Now we’re facing problems that few guys are able to connect to Exchange using Outlook 2000 (as exchange clients) while others cant. I feel its due to License issues.

Exchange server is working fine as all users can access emails thru Outlook Web Access (thru IE).

In Control Pannel – License Manager – its comes as MSDN.

Is there any way / a reg hack to change this ? We have original NT & Exchnage CDs & licenses.
Akash