How can you create pop up messages in a batch script?

With regard to LittleBobbyTable's answer - NET SEND does not work on Vista or Windows 7. It has been replaced by MSG.EXE

There is a crude solution that works on all versions of Windows - A crude popup message can be sent by STARTing a new cmd.exe window that closes once a key is pressed.

start "" cmd /c "echo Hello world!&echo(&pause"

If you want your script to pause until the message box is dismissed, then you can add the /WAIT option.

start "" /wait cmd /c "echo Hello world!&echo(&pause"

msg * "Enter Your Message"

Does this help ?