I use this free software to convert M4b to MP3. It will do either m4a or m4b.
ManiacTools, Free M4a to MP3 Converter.
http://www.ManiacTools.com
I use this to split MP3 to smaller files.
Splitter
http://www.nch.com.au/splitter/index.html
And I use this software to join MP3 when there are too many files.
Meda MP3 joiner
http://www.medafan.com/mp3-joiner/
Something else you may run into: do not have long file names.
I have 5 Sandisk Clip Sports and use them every day or Audio books, Radio shows, and Podcasts.
Just to be picky, it is a Sandisk Clip +
