I know this may not be the most helpful reply you are going to get, but it is probably the most realistic.

The fact is porn and the internet go hand in hand, yes you can block IPs, block specific words in your search, etc., but for everyone of you out there who is trying to rid their computer of porn, there is 100 people in the world paid to get around whatever tact you have come up with to stop it.

Best advise I can seriously give you is to get over it. Yes it's annoying, yes it clogs up the screen whilst searching for what you are really looking for, but unfortunately that's the way it is. You'll have as much luck channel surfing the T.V. to avoid advertisments as you will avoiding porn when downloading files on a P2P network.

Sorry for the negativity
ZB