Not all vidoes being added to library

[cyclocross]

So I added my Movies folder to WMP 12 but for some reason it's only showing 66 of the 75 movies in this folder. All 75 were encoded to MP4 using Handbrake on identical settings so there's no differences between the files. Any ideas why 9 of the files refuse to show? They play just fine in WMP 12 - I just can't add them to the library (which in turn means I can't watch them on my TV via my 360)

 

[Zidane24]

Could be due to DRM on them

Just a guess but it seems probable