MPAA/RIAA Proof

Earlier there was a discussion in /g/ about how to protect your movies/music/anime that you may of hypothetically downloaded illegally from the MPAA/RIAA.  After reading the topic I have a few questions about some of the statements made.

1. One poster mentioned that if you don't download 100% of a torrent (say, Dirty Harry) and delete it after you finish watching it, they can't pin anything on you since you technically didn't have the entire thing.  In some sites like Demonoid, they usually come with a little .txt saying "downloaded from Demonoid", if you were to uncheck that download in utorrent and just download the movie files, would this method work?

2. Is linux more secure than windows when it comes to this?  I know it's generally more secure than windows, but when it comes to encryption/secure file deletion is it superior to its windows counterparts?  Or is it plagued by the same pitfalls as windows is when attacked by nerds armed with data retrieval software?

downloading music and movies from file sharing networks is not illegal.
true, but that doesn't make the act of copyright infringement any less illegal
if the mpaa/riaa can't convince a jury that you did anything wrong, they can't legally do anything.
that doesn't make the act of copyright infringement any less illegal