To add or change the values of environment variables

Open Computer Management (Local).
In the console tree, right-click Computer Management (Local), and then select Properties.
On the Advanced tab, click Environment Variables.
Select a user in the User variables for list.
Click the name of the user or system variable you want to change or delete.
Click New to add a new variable name and value.
Click Edit to change a current variable name and value.
Click Delete to remove a variable name and value.