I tried to upgrade the firmware, but never got the upgrade screen. I have the HXF file in the root directory. I press and hold the - key, then press the play pause button, but it only turns the player off. I'm just glad I didnt brick my brand new player.
Can the 767 use a battery pack? Music doesnt sound too bad on the 767 from the songs I heard on the player. Wish it would play ogg files!
Make sure that your player is turned off and then push down on the buttons.
As for the battery pack, the player can use it to run off, but it can't charge of it (unless you can find an adapter to connect via USB to the players power adapter input).