How Do i FIx my MSN Messenger?

when i click on msn messenger a message appears that says: Messenger has encountered a problem and needs to close. We are sorry for the inconvenience. and it gives me two options the one on the left says debug and the one on the right says close...when i click debug nothing happens. please help me
i have a gateway pentium 4....from about 2002 or around there... i have windows xp home edition