Windows Messenger v4.0 ???

Hi, I have a small 10 computer network. All of the clients are on Windows 98. We use messenger for inter-office e-mail, I have a user who uninstalled Windows Messenger v4.0 on her local machine. Where can I find a copy of the program. Everything on the MS web site is v4.7 (for XP). Is the program on the original W98 CD? I ran setup from the W98 upgrade and that did not install messenger v4.0 Thanks GL.