It is quite rare that I use Telnet these days, so it took a long time for me to notice that by default it was not packaged with Windows Vista. This is also the case for Windows 7. Telnet is very insecure and whenever you have the choice you should always use SSH, so more than likely this was an attempt to make Windows more secure by default.
With that being said, you can quickly re-enable Telnet by following these steps:
- Control Panel
- Programs And Features
- Turn Windows features on or off
- Check Telnet Client
- Hit OK
After that you can start Telnet via Command Prompt or through the Start Menu.