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Using the add-on tool Setx.exe
It is not part of the standard Windows XP setup but a command-line tool called setx.exe is included in the Windows XP Service Pack 2 Support Tools. This tool extends the set command so that permanent changes in the environment variables can be made. For example, to add a folder C:\New Folder to the path, the command would be
setx path "%PATH%;C:\New Folder"

Scripts for Listing Environment Variables
The "Set" command can be used in a command prompt together with a redirection to a text file to make a list of the current environment variables. The command might be
set > C:\env_list.txt file
The file name "C:\env_list.txt" can be replaced by any of your choice.

Microsoft also has a VBScript that lists environment variables on this page.

Registry Keys for Environment Variables
For those who are experienced with editing the Registry, there is another way to make changes in environment variables. User environment variables are stored in the Registry in the key

HKEY_CURRENT_USER\Environment

System variables are found in the key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Cont rol\Session Manager\Environment

Note that any environment variable that is in the form that needs to be expanded (for example, %PATH%) must be stored in the registry as a REG_EXPAND_SZ registry value. Editing the Registry is primarily for scripts used by systems administrators and is not recommended for the average PC user.