The basic functions of your mouse and keyboard should work without having to install any additional drivers
. Assuming they are PS2 or USB that is, and not wireless. I can't speak for other brands but my wireless Logitech keyboards and mouse work in windows 7, even during the install process. If your mouse and keyboard have some custom keys you may have to install the manufacturers software/driver
to get them to work. The drivers delivered though windows update are just your basic drivers, and are supplied by the original manufacturer. It could be that the manufacturer of your keyboard and or mouse never submitted drivers to Microsoft and are just relying on the Windows basic driver to get you going.