Is there many different mp4 files?
Kind of. MP4 is a format, but there are settings you can change in MP4. Like I can play some MP4 videos on my ipod, and others I can’t. It all depends on the settings. Format Factory has a lot of setting you can change, so I suggest getting this. There are 2 Sony Ericsson specific MP4 options so I’m pretty sure 1 will work. Download from: http://www.formatoz.com/ I use it and love it! I highly recommend it.