Another little hidden tool in Windows XP, accessible via the Start Menu Run line is the System Configuration Editor. Accessed by typing “sysedit” at the Run prompt, the utility opens up the following files for editing:

System.ini - Initialization file initialize system settings for the computer such as the fonts, keyboard, language and various other settings.
Win.ini - used to load various settings each time Windows boots, for example the communications drivers, wallpaper, screen saver, languages, fonts, etc… are loaded each time the win.ini is initialized.
Config.sys - used for loading various drivers and other items. Not used anymore in later versions of Windows, but is still there.
AutoExec.bat - used to load up software automatically when booting, but again, this is from the MS-DOS and Windows 3.x days.

Be careful making changes by hand in these files.