Setting environment variables
Environment variables are strings that contain information such as drive, path, or file name. They control the behavior of various programs. For example, the TEMP environment variable specifies the location in which programs place temporary files.
Any user can add, modify, or remove a user environment variable. However, only an administrator can add, modify, or remove a system environment variable.
Using System in Control Panel, you can customize the following variables:
User environment variables for logged_on_user_name
The user environment variables are different for each user of a particular computer. The variables include any that are set by the user, as well as any variables defined by programs, such as the path to the location of the program files.
System environment variables
Administrators can change or add environment variables that apply to the system, and thus to all system users. During installation, Windows Setup configures the default system variables, such as the path to the Windows files.
Add or change the values of environment variables
System Properties overview