can I inhibit my kids from getting copyrighted files?

[scaredparent]

Have a couple questions.
1. I've recently been accused by my internet provider of copyright
infringement on some Harry Potter mp3 being on my PC and are threatening
termination of my service. I CANNOT, for the life of me, after doing
multiple PC searches, find anything resembling the filename they say they
found. It looks like my teenagers don't even have the shared folder
configured in Limewire. My question is: if my teenagers just did a
search of Harry Potter would that trigger that action by my internet
provider?

2. What actions in Limewire can I take to inhibit my teenagers from
doing something like that? If there isn't anything I'll have to remove
Limewire from my PC because I use it to connect to work and need the
internet connection. Really would rather not remove your software. My
kids like it a lot.

3. Does the PRO version of Limewire help me at all with these
concerns?

Really appreaciate ANY advice anybody can give me here. Right now I'm
not sure I'm buying my internet provider's story.

Thank's very much for your time!