And what about VLC player, many use it with Win 7...Gstreamer is commonly used with variants of Linux and I have tried it in different versions of Linux but not with Windows....
There are a lot of options so you will have to try a few, but you could look at Clementine. This is (says Wikipedia) 'a cross-platform free and open source music player and library organizer. It is a port of Amarok 1.4 to the Qt 4 framework and the GStreamermultimedia framework.' I've not tried it myself.
Otherwise, the AlternativeTo site is a handy place to look for alternative programs. In this case, look at http://alternativeto.net/software/rhythmbox/

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