a) Bittorrent is not a music site
b) Bittorrent is not a `music software`
c) Bittorrent is the advertised name of Bram Cohen's mainline client. It is also the name of the protocol used by this client as well as other Bittorrent clients.
d) `Safe` is a relative term. It's never `safe` to break the law, if that's what you're asking. Piece verification system in the Bittorrent protocol is effective though, if that was what you meant. It is (virtually) impossible for your finished copy of the file to differ from the original.
e) Vista crashing is probably unrelated. Vista crashes every few days for me, which is only slightly more often than XP. That's the norm with just about any Windows operating system.