Hi, I would recommend ogg or wma for the smallest file size without losing quality. For converting files, I use
dBpowerAMP MusicConverter because its fast and free. If you have pocket pc 2003 then you can download the wma 9 codec for dBpower AMP and get even smaller file sizes. So If you do have ppc 2003 then use wma 9 with windows media player or if you have ppc 2002 then use Ogg or wma 8. Also if you look in the help file of dBpower AMP there is a good guide to help you convert your files. As for the bit rate to encode the files, I would use 128Kbps or 192Kbps if you have good ears.