Password Protected LockUp is an excellent system-tray utility you can use to restrict access to your PC. It's attractive, secure, and very easy to use. It starts automatically with Windows and optionally locks your desktop upon loading. It hides your desktop at the same time and provides a scrolling message that you can edit as you like. You can have the program power down your monitor after a selected period of 'lock-up' time and even set start/stop times for other users to limit their access to your PC. Optionally, it can show LockUp Screen or launch Windows Screen Saver. Also it has special Screen Saver. Besides, it has the network client validation feature for Windows logon.
