I was on my Microsoft Windows 10 desktop computer last night and wanted to telnet into a Linux server. I started a terminal window also known as a command prompt windows. I typed telnet servername and got an error. The telnet service isn’t installed. When I installed Windows 10, I left the default settings and the Unix services didn’t get installed. To install them or any other Windows built-in programs and services, open Control Panel then Programs and Features. Then open “Turn Windows Features on and off”. You will be presented with a list of options to toggle on or off like Internet Explorer 11, Hyper-V, and Telnet client. So if something in Windows is missing that you know exists, check the Windows features to see if it is off.