I think you are prolly using an older version of mIRC. In mIRC, click on the "About" button to see what version you are using and then go to
www.mirc.com/get.html to download the most recent version, 6.12
Regarding filesharing, please read
this thread Many networks no longer allow channels to exist for the primary purpose of filesharing, including mp3s, so the channels were likely closed down.
