I got 7-Zip installed and for file types, all of them are selected to be opened with 7z. But .zip archives still don't associate with 7z. Look:

The .zip archive is handled by Windows if I double-click it. I already tried opening the 7z preferences and unchecking .zip then saving and then checking off .zip and saving again but that's doesn't help.
Don't mind the fact it says Vista there. I'm on Windows XP SP2.