Force Black and White Photoshop Plug-in

Force Black and White Photoshop Plug-in is a tool to manage images in black and white as you  transfer them to indexed color. It is free. When installed in Photoshop's Plug-ins folder, the Force Black and White Extension Plug-in forces Photoshop 5.0.x to include pure black at the beginning of the palette and pure white at the end of the palette whenever a document is converted into the Indexed Color mode using the adaptive palette. Images converted in this fashion will work in the applications that require pure white and pure black palette entries, but the colors chosen will be slightly less optimal for the image since there are two fewer available.