Environment variables control the behavior of various programs.
Any user can add, modify, or remove a user environment variable. However, only an administrator can add, modify, or remove a system environment variable. There are also some predefined environment variables that are set when the user logs on. Managing NT Environment Variables NT Environment Variables Environment variables on an NT machine hold a wealth of useful information that administrators can access to make logon scripts and other scripts automate daily tasks. Registry key stores static user variables.