Open a socket connection to the Tor process's control port and send the desired plaintext commands. You can't natively open sockets with a windows batch files, but you can with Monad (renamed to PowerShell), the new command shell and scripting from Microsoft. Although it's marketed for Windows Vista, it works with any NT-based OS (e.g., XP, NT, Server 2003, etc) and is a free download. WIth PowerShell, you have native access to any .NET and/or COM object--including socket wrapper objects.
http://en.wikipedia.org/wiki/Windows_PowerShell