If you do not need this for various reasons, it can be annoying when it comes up every day.
Some people have said you need to resinstall Lotus Notes to remove this functionality. This is not true:
Close down Lotus Notes.
For Win2K (Microsoft Windows 2000) you can stop and disable the password service by closing Lotus Notes and doing:
Start -> Control Panel -> Adminstrative Tools -> Component Services -> Services (Local) -> Lotus Notes Single Signon. Change the startup type to disabled by seleting the line then right clicking on options. Stop the service by clicking on stop. Restart the Notes client and you will be prompted for the user password normally.
For Windows XP you can stop the service by:
Start -> Control Panel -> Performance and Maintenance -> Adminstrative Tools -> Component Services -> Services (Local) -> Lotus Notes Single Signon. Change the startup type to disabled by seleting the line then right clicking on options. Stop the service by clicking on stop. Restart the Notes client and you will be prompted for the user password normally.