Spidey's jerking you around a bit because a lot of professional folks frequent these forums and they don't appreciate the idea of pirating software.
The answer is that you can't hide your IP address, period. For their computers to connect to yours, and vice versa, they have to know your IP address.
That's why the most successful way to catch these guys is simply to make a high volume file available, like the latest song or newest movie, then record IP addresses that download it from you.
The only way to keep from getting caught is not to do it. That would be my suggestion.