Foobar2000 is a bare bones media player for MP3, WAV, OGG and other media formats (may require plug-ins). It doesn't require installation. You can just unzip it and go. At less than 400 KB it won't take up much hard drive space. And it won't tax your system resources. It looks rather plain, but a quick glance at the preferences shows that it has quite a few features thus making it a very capable media player.
Mr magoo says read more for the thousands of bug fixes :)
Download: foobar2000 v0.6 with installer
News source: foobar200 web site