ahhh torrents, save me a fortune they do :P
bitorrent and media codecs aren't neccesarily going to work out of the box for slackware infact with my experience of slackware 10.1 it was less so than other distros.
a quick google gave me this http://ubuntuguide.org/
note there are sections devoted to azureus (my favourite bittorrent client) and media codecs...
give that guide a shot, you might pick up some other nice bits too, once you have tried you can always post your specific errors here for people to help you fix them.