What to do?
1. Do not EVER EVER download anything connected to or using
BitTorrent. It's been the bane of Windows users for a long time.
2. Do not EVER download bootleg/pirated copies of anything. It's
illegal and it's a good way to get a virus.
3. Consider buying an anti-virus application like Intego's
4. Do nothing and you're at your own risk.
5. So far, you're probably not doing 1 or 2, so for you it's not much
of a worry.