Telnet Client is not installed by default on Windows 7,you can follow one of the below method to enable / install telnet client in Windows 7.
Method One:Install / Enable telnet by using command line command
1.Open a command prompt window. Click Start, type cmd in the Start Search box, and then press ENTER
2.Type in the below command and press ENTER
3.If prompt by User Account Control , confirm that the action it displays is what you want, and then click Continue.
4.Done,now you have enable telnet in windows 7
Method Two:Install / Enable telnet by using Turn Windows features on or off
1.Click Start, and then click Control Panel, then Programs and Features
2.On the left pane of the Window ,click Turn Windows features on or off.
3.In the Windows Features list, check Telnet Client, and then click OK