I believe the cartoon you are thinking of is "The Proud Channel". This
episode was aired Oct 5, 2001.
"Some media watchers are crying "foul" for Disney's use of a pre-teen
television cartoon to convey an anti-file-sharing message. A recent episode
of Disney's "The Proud Channel" used a plotline where Penny Proud is
introduced to file-sharing by a friend. Penny develops a liking to
downloading music from the Internet. The trouble starts when a musician
calls the police after receiving a smaller royalty check than expected. The
police - who surround Penny's house - threaten to arrest her causing her
parents to take away her computer. But if that's not enough, her downloading
music puts the local record store out of business as well."
Google's cache of http://owa.benton.org/listserv/wa.exe?A2=ind0110&L=benton-compolicy&F=l&S=&P=60
"In a 2001 episode of "The Proud Family," a Disney Channel cartoon
series, the teenager Penny gets addicted to filesharing after she is
shown the wonders of a Napster-like program called EZJackster."
"The Disney Channel cartoon series The Proud Family aired an episode
on October 5 entitled EZ Jackster . In the storyline, EZ Jackster is a
Napster-like site, and the show's little heroines get addicted to the
service and play a part in the downfall of the music industry."
The Register: Disney cartoon lambasts evil music-sharing
cartoon "downloading music" internet
"The Proud Family" "downloading music"
I hope this is helpful. If you have any questions regarding my answer,
or believe this is not the cartoon you are thinking of, please don?t
hesitate to ask for further assistance before rating.