Windows Live Messeger/Registry Key Problem

For some messed up reason I can't update or uninstall WLM. Everytime I try I get an error the tells me that there's an error with a certain registry key, so I go to the key in regedit and when I click on it, it tells me that I don't have permission, so I give myself some and click 'Apply' but then it gets me a message saying I can't give myself permission.

So I have this key that I can't delete, edit, or give myself permission, and because of it I can't install MSN.

http://img80.imageshack.us/img80/8031/50681654.png
Here's the error I get when I try to install MSN 8.1. (An old version)

Also, I use Windows 7.