If you start Notes 6 on Windows 2000 logged on as a non-admin user, you will get an error:
"You cannot use the Administration program while the Domino Server is running. Either shut down the Domino server (but keep the file server running) or choose the icon labeled 'Lotus Notes' instead"
Notes 6 is installed by default in Program Files folder, which has only Read/Execute permissions for regular users.
In order to be able to run Notes 6 without administrative rights, add Modify permission on the lotusnotesdata folder for the local Users group.