Changing from iso-8859-15 to utf-8

I seem to have all my old posts in iso-8859-15, and the few new posts I made BEFORE importing in utf-8.

Any way of changins the encoding on all my posts? I have this problem every time I set up a new WP install. I’d like to change it to utf-8 so I don’t hafta remember why the hell all my special characters look like a questionmark every time I need to reinstall WP for various reasons…

It’s getting on my nerves, really!

My language is Norwegian by the way.