MS Windows Messenger v5.0 for Windows 2000/XP/2003
http://www.microsoft.com/downloads/details.aspx?FamilyID=77c3799f-6388-4193-8002-be55584c1ac1.

MS Windows Messenger v4.7 for Windows XP
http://www.microsoft.com/downloads/details.aspx?FamilyID=b475d2d1-6266-4d82-bf78-14597545a6b4.

Windows Messenger v4.6 for Win9X/ME/NT
http://download.microsoft.com/download/8/6/7/86768d83-097e-4ae4-a09d-5d24bd77ff9e/mmssetup.exe.