The default Telnet Server greeting, prompt, and shell are controlled by the %SystemRoot%\System32\Login.cmd file.

The default script is:

@echo off                              rem                              rem  Default global login script for the Telnet Server                               rem                              rem  In the default setup, this command script is executed when the                              rem  initial command shell is invoked.  It, in turn, will try to invoke                              rem  the individual user's login script.                              rem                              echo *==========================================================

echo Welcome to Microsoft Telnet Server. echo *

========================================================== cd %HOMEDRIVE%%HOMEPATH% /d
You can alter the echo Welcome to Microsoft Telnet Server. to echo Welcome to MyCompany Telnet Server on %ComputerName%.

You can add the following at the end of the file to change the prompt:

prompt %computername%:$P$G.

NOTE: You can edit this file in Notepad.