Vista comes with a telnet client and server. They are not enabled by default. If you would like to use either of these features, just follow these steps…

 
1. Click the Start Orb
2. Click Control Panel
3. Select Programs
4. Select Turn Windows Features on or off
5. May need to confirm the UAC
6. Wait…
7. Click the checkboxes beside the telnet client or server.

8. Click OK

from http://www.tech-recipes.com/rx/2050/vista_install_enable_telnet_client_server/