By default, Vista doesn’t install the Telnet client. The client is for text-based communication with remote systems. You can install it by following these steps:
1. Click Start then select Control Panel.
2. Select Programs and Features.
3. Select Turn Windows features on or off.
4. Select the Telnet Client option.
5. Click OK.
6. A dialog box will appear to confirm installation. The telnet command should now be available.
If you feel that this step taking time, you may refer to the command as below and run it from cmd(command prompt).
start /w pkgmgr /iu:”TelnetClient”