Ever want to set or remove Windows environment variables permanently within a command file, so you can use it in other command sessions? Use setx en reg !
setx.exe is an application that comes with the Windows XP Service Pack 2 Support Tools (not sure if it comes standard in Windows Server 2003) and inserts the environment setting in the Windows Registry (HKCU\Environment). The environment setting however will not be available in current open sessions, only in new opened sessions.
The reg command is available without some Pack (at least on XP). You can use it to remove registry keys, but the environment setting will not removed from current open sessions. You could also use it to add environment settings…
To add entries
setx oracle_sid prod reg add HKCU\Environment /v oracle_sid /d prod /f
To delete entries
reg delete HKCU\Environment /v oracle_sid /f