Telnet is not recognized as windows command

There are 2 things that you can do.
1) Install Telnet from the Windows feature
Go to Start -> Control Panel -> Programs -> Turn Windows feature on or off
Under feature section, find Telnet client ensure that it's ticked (if it's not).
Once (1) is installed, if you still encounter telnet is not recognized error, you can proceed with (2)

2) Go to Environment variables
Right click on my computer, select Properties, on the left side select Advanced System Settings.
Under Advanced tab, click Environment Variables, under System variables section, find the Variable = Path, ensure that C:\Windows\System32 is there. If it's not there, just append it.
Then click OK.

You should be able to run telnet commands now.