My favorite PDA music and movie player has officially changed its name from Beta Player to TCPMP (The Core Pocket Media Player). TCPMP is an open-source media player for Palm and Windows Mobile devices.
I have used this program pretty much since I first purchased my Axim. I've never had encountered a problem and it beats the Windows Media player included with the Axim by a MILE. I also prefer it to the RealPlayer that is included with my Treo 650. If you would like to try it out, you can download the Palm version and the Windows Mobile.