Exchange SP3 problem

I recently tried to install SP3 to an Exchange Server running on a Windows
2000 server (sorry I didn't get the Windows Server SP#). The installation
keeps hanging on "starting license service". I have tried a reboot to no
avail. Any suggestion on what might be causing this and how I might get
around it? I know how to stop and start services from a command prompt in
Windows 2003 and I wonder if it will be the same in 2000? I cannot find that
documentation for Windows Server 2000. Will the server run without the
license service running? I have had no other problems with this server and
only required the SP update so I could install Exchange 2007 in another
domain in the same forest.
Thanks
Sharon