Like Windows 7 and Windows Vista, the Telnet client isn’t installed by default.
In Windows Server 2008, you can install it via the Server Manager GUI tool, but it is often quicker to install it via a command prompt/terminal.
So, open a cmd.exe session and run the following:
servermanagercmd -install telnet-client
And that’s it – once the command has completed, telnet.exe will be available from a command prompt.