‘telnet’ is not recognized as an internal or external command

By default, telnet client or telnet server is not running in windows vista. we may need to enable them.

just enable it : Click Start, Control Panel, Programs, and then Turn Windows Features on or off. In the list, scroll down and select Telnet Client. Click OK to start the installation.

Thanks http://trycatch.be/blogs/scratchthesurface/archive/2007/04/15/vista-telnet-is-not-recognized-as-an-internal-or-external-command-operable-program-or-batch-file.aspx