Paul, Google is your friend . From http://www.fileinfo.net/extension/m4b You need to have ITunes, I reckon. thereafter, the file type may play in several players. Now the excerpt cometh: .M4B File Extension Run a free scan for .M4B file extension errors. File Type MPEG-4 Audio Book File Category Audio Files Common? No File Description Audiobook file based on the MPEG-4 container format; typically compressed with .AAC encoding; nearly identical to a .M4A file, but denoted as an audiobook and can be "bookmarked" by supporting audio players. The M4B extension is used by audiobooks downloaded from the Apple iTunes store; iTunes audiobooks are copy-protected using Apple's FairPlay DRM and can only be played on authorized computers using iTunes. Program(s) that open m4b files Mac OS Apple iTunes + iPod Microsoft Windows Media Player VideoLAN VLC media player Windows Apple iTunes + iPod Microsoft Windows Media Player VideoLAN VLC media player Linux ----- Original Message ----- From: "Paul Halligan" <tigerone@xxxxxxxxxx> To: <vicsireland@xxxxxxxxxxxxx> Sent: Tuesday, November 04, 2008 9:14 PM Subject: [vicsireland] m4b file types Blankhi folks have downloaded some audiobooks which have a unusual file type, m4b. none of the players i have will play the books i.e. real, winamp or wmp. i used real to play m4a files . are m4b files a relation or does anyone know how i can get these books to play. thanks aforehand Paul H