Each operating system has its own unique system files. However there are two system files that can be found in all the Windows based operating systems. These are the:
The CONFIG.SYS(Configuration File)-- file is a text file that contains commands that configure your computer's hardware components (memory, keyboard, mouse, printer and so on.) The CONFIG.SYS file is run first when your PC boots.
The AUTOEXEc.BAT(Automatic Execute)-- file is a batch program that is run immediately after the CONFIG.SYS file and contains commands that you want to execute when starting your PC.