1) GarageBand works, but I'm not sure for Windows. I'm on a Mac.

2) iZoo fits that bill for me. I also love Chess, but that's personal.

3) Too broad to answer.

4) I'm currently using iSpazio's Mac OS X and Vista Perfection theme. These require Categories and Poof to arrange. You may end up messing up your Springboard if you're not careful, so take note.