I can't download MSN messenger.

Hello,
I have windows vista, and i used to have the second latest version of MSN messenger. I tried updating it to the latest version, but i couldn't. I when i went to help, it said to uninstall and reinstall. Well now i can't even use a later version because it says i need the latest version. I am pretty sure that its some setting on my hp laptop, some security setting perhaps. But i really don't know. I've tried everything that comes to my mind, but i havent been able to get it, can any one help? Perhaps know what i need to do?