Glad you found the "guide" useful!
It was WINRAR 3.62.
I don't back up the firmware, I just reload it when necessary as described in my web page. I back up the music files just by copying them to a separate area of my hard drive. I seem to avoid the NO FILES and deleted files problems if I don't change the play list or add / subtract any files once I have started playing any music, other than by reloading the firmware (reformatting at same time) and recopying the music files from the backup area on my hard drive. My suspicions on this subject are outlined in my web page, which is at:
http://www.tooby.demon.co.uk/Log/Netac.html
Hope this helps!