If you want to use your Pocket PC as an MP3 player you'll probably want to find something a little more touch-friendly than the default Windows Media Player.
Nitrogen could be just the ticket, as it enables you to easily access and play songs stored on your device (or on the memory card) without any hassle. The program's user interface is much more finger-friendly than Windows Media Player, complete with chunky menu buttons and an iPod-style scroll wheel for flicking through your tracks.
MP3 playback quality in Nitrogen is pretty good, and the app uses a MAD decoder for superior sound output. There's a separate 11-band graphic equalizer that lets you tinker with the audio and you can create your own presets - though Nitrogen doesn't come with any built in.
Nitrogen is still in Beta development stage and it's far from a polished product. One thing I'm hoping for is the addition of a few more features. There are a few neat tools such as a sleep action, softkey mapping and a blank screen mode to save power. However, the application lacks the more meaty functions like album art, playlist support, ID3 tags or Today screen integration.
That said. as a work in progress, Nitrogen looks promising and is certainly much more conducive to touchscreen use than Windows Media Player.