I for the first time in my life downloaded a little tool, loved it and payed for it.
The name of the tool (and site is): All To MP3 Converter
This tool lets you convert different music formats from and to each other. This is as easy as to right click a file and choose convert. There is also a nice little GUI that does the same thing but lets you decide more details.
It opened up about 100 WMA-files that i could listen to since i am using [RockBox](http://www.rockbox.org/) on my H320 IRiver