Windows Live Messenger (or MSN) isn't working properly. How should I fix it?

Okay, so I use Windows Live Messenger (or MSN, whatever you want to call it) to talk to some friends online. But for some reason, it keeps giving me this older, not very good version to use. I used to have the good, newer version, but it randomly switched to this older version, and now I can’t get rid of it. It’s not very user-friendly, it’s slow, and it’s difficult to use. How can I get the newer version back?