Try uninstalling both MSN Messenger and Messenger Plus! 3
Start > Control Panel (the classic view) > Add or Remove programs
Then select Messenger Plus! 3, and uninstall it, do the same for MSN Messenger...
Then redownload and install MSN Messenger, and then after Messenger Plus!
The direct links are
MSN Messenger
http://download.microsoft.com/download/0/9/a/09a7...36bb52/SetupDl.exe
Messenger Plus!
http://download.msgplus.net/files/MsgPlus-301.exe