Import movies already on computer into iTunes I have a bunch of movies/TV programmes on my computer that I want to transfer to an iPad. As far as I know, the only way to do this is to first add them to iTunes (on a computer), then synch iTunes with the iPad.

Some of these movies are .avi files and others are .mp4 files. I've selected the Films section of the iTunes Library and opened the "Home Movies" tab. I've tried several ways of add the files including:


The "Add File to Library..." menu item (in the file menu)
The "Add Folder to Library..." menu item (in the file menu)
Dragging the file from windows explorer and dropping it into iTunes


For some reason this fails for all the files except one. The one that works is an .mp4, but strangely none of the other .mp4 files (or any of the .avi files) appear in iTunes after I try to add them to the library.

Is there some reason why this one particular .mp4 would work but not others? Is there another simpler way to transfer these files to the iPad? I'm using iTunes 11 on Windows.
This is from the Apple Support site:


  What video content works with iTunes and mobile devices?
  
  iTunes:
  
  
  Video content purchased from the iTunes Store. 
  QuickTime and MPEG-4 movie files that end in ".mov", ".m4v", or ".mp4" and are playable in QuickTime Player. 
  Video podcasts.
  iTunes Digital Copies. 
  iTunes Store Movie Rentals (Requires iTunes 9 or later).
  


I've had luck converting non-compatible video for iTunes and i devices with Handbrake, a multi platform, open source video converter.