I use Audacity which is a free Open Source audio editor it converts Ogg files to wav or Mp3 (although you'll need an additional (free)plugin for Mp3 conversion. It's a very good editor.
http://audacity.sourceforge.net/
failing that you could get Irfanview a free media viewer which with an additionally installed free plugin, will play Ogg files without the need to convert them
http://www.irfanview.com/