I think that installs only xmms-specific plugins to handle mp3 playback. To get all the other players work as well, you'll have to get
1) plugins that are specific for a player (like xmms for example)
2) engine plugins/codecs, that work for the engine and thus for every ("player")app/front-end that uses that engine
There are two main choices for an engine, Xine and GStreamer. No idea which one Fedora 7 uses by default, but probably either of those (could be something else also). Both work well, but it seems at the moment Xine is liked more (note: it's not just the player called Xine, or xine-ui like most think, but it's really an engine too). For example Amarok, Totem etc. are merely front-ends that use some engine (in Amarok you can change it, but Totem needs to be recompiled or another Totem-version installed to "change" the engine it uses; it's configured at build time). For Xine you need the extra plugins library (libxine-extrasomething or equal) or for GStreamer you need a few gstreamer-plugins-something packages. Everything available at online reposities, probably at Livna too. After installing the right codecs/plugins/whatever you want to call them (note: the right ones for the engine you want to use!), every app using that engine is able to play the files the plugins allow. For Xine you might also want to install (from mplayer's site for example) the Win32 codecs, which allow the playback of several extra formats (wmv, wma, ...)also.