Long, but most thorough, method
Start by completely uninstalling everything.
Properly uninstalling a program is done by going to your Windows Configuration Panel and selecting "Add/Remove Programs".
1) Uninstall any Messenger related addon (this includes stuff like patches, SmileyCentral, SweetIM, MSN Content Plus, etc)
2) Uninstall Messenger completely!
3) In Windows Explorer (
*) navigate to "C:\Program Files\MSN Messenger" and completely remove that directory and everything in it.
4) In Windows Explorer (
*) navigate to "C:\Program Files\Windows Live\Messenger" and completely remove that directory and everything in it.
4bis) If you really want to clear everything (note: this will also remove all your settings), then follow steps 3 to 5 from the intructions given in:
"
CookieRevised's reply to Windows Live Messenger BIG PROBLEM!".
5) Now reboot your computer
6) Redownload Messenger and install it
MSN Messenger 7.5 can be found
here.
Windows Live Messenger 8.0.0812 can be found
here.
Windows Live Messenger 8.1.0178 can be found
here.
Windows Live Messenger 8.5.xxxx (beta) can be found
here.
7) Redownload Messenger Plus! and install it
For MSN Messenger 7.x you need Messenger Plus! 3, found
here.
For Windows Live Messenger you need Messenger Plus! Live, found
here.
Short, but not always working, method
1) Close Messenger completely by right clicking its system tray icon and choosing "
Exit".
2) Manually remove the file "
C:\Program Files\MSN Messenger\msgslang(2).dll". (
*)
3) Install Messenger Plus!.
links updated