Notifies the OS and all running applications that environment variable(s) have changed.
ErrorLevel is set to 1 if there was a problem or 0 otherwise.
Refreshes the OS environment. Similar effect as logging off and then on again.
For example, after making changes to the following registry key on Windows NT/2000/XP, EnvUpdate could be used to broadcast the change: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session