make sure you log into your pc as Administrator
also try this:
1.Exit MSN Messenger Program completely
2.Click on Start, then Run, type: "regedit" (Without Quotes)
3.Navigate to MyComputer\HKEY_CURRENT_USER\Software\Microsoft\MS NMessenger
4.Click the MSN Messenger Key (Click Once). Go to the Edit menu and select Delete
5.Delete the MSN Messenger folder from c:\Program Files (Replace C: with your system disk if it is something other than C)
6.Install MSN MESSENGER
still not working then go here:
http://msntech.webhelp.com/msntech/
ask a MSN techie for free live