By default, Telnet is disabled in Windows 7. You can enable it by,
Programs And Features
Turn Windows features on or off
Check Telnet Client
After that you can start Telnet via Command Prompt.
Open a command prompt window.
Click Start,type cmd in start search box, and then press Enter.
Type the following command
If the User Account Control(UAC) dialog box appears, confirm that the action it displays is want you want, and then click continue.
When the command prompt appears again, the installation is complete