I think Apple stopped selling iTunes tracks with embedded DRM (m4p) in 2008. Since then all tracks sold in the iTunes store do not have DRM (m4a). It should not be necessary to use any DRM removal software on iTunes tracks purchased since 2007?
Try using Folder Mode to test the compatibility of your tracks with your Clip Sport Plus player.
in my experience, the SanDisk players play more nicely with mp3 tracks compared to m4a tracks.
