From RJL Software:
This security application will lock your desktop from unwanted users. There are several display options you can choose from, a totally black screen, capture the desktop, or display a specified bitmap. There is a setup screen where you can define the password, display type, mouse options, and more! There is no installation required, just click on Black Screen and the first time it is launched it will configure your system. Perfect program to secure you desktop with no hassles. Black Screen has a very ingenious mechanism that allows users to enter their password quickly to exit this security program.