Usually the common M4V files are without any protection, they can be used freely. But if you purchase the M4V files or make itunes rentals from iTunes Store, these M4V files are DRM-protected, and likewise you can't enjoy them freely.
Convert unprotected M4V
There are knids of video converter tools to convert unprotected M4V files, like Kigo Video Converter Pro, Ultra QuickTime Converter, Daniusoft Quick time Converter and so on.
These M4V Converter tools, as powerful QuickTime M4V converter, are with the features of M4V to WMV converter, M4V to MP4 converter, can help you convert M4V to AVI, M4V to WMV, M4V to MP4, M4V to MPEG easily, and also convert QuickTime MOV, QT, MP4, M4V files to AVI, DivX, Xvid, MPEG1, MPEG2, VCD, SVCD, .VOB, WMV, ASF format with high quality.
Convert DRM-protected M4V
So when we encountered ""I purchased videos on iTunes, but I can't play them on my video player, because they are in some 'protected' M4V format that only works on iPods, iPhone. How can I convert iTunes videos to unprotected format so I can play them on MY portable video device?"
For DRM-protected M4V, are always iTunes M4V files producted by Apple Inc. Apple, provider of the popular iTunes service, has limited the software so it will copy purchased videos (M4Vs) only to video iPods -- also an Apple product. Some say this protects the digital rights of the copyright owners, but nobody disputes the fact that it helps Apple to keep a stranglehold on the portable player market.
If you want to solve the problem - converting DRM M4V, you can use M4V Converter Plus, it is a suitable DRM removal, you can easily convert the iTunes DRM M4V to unprotected M4V, MOV, MP4. If you want to convert to other popular format, you can still use a common video converter to get your goal.