I believe I have
this page properly coded (Sparky's posted code in another thread) to prompt the user to download the proper plugin if they don't have a player for mp4 files.
The problem is that usually movie files are linked directly to the movie instead of being embedded in a page.
This is why I'm stuck in the stone age of using mpeg-1 (mpg) files since they play in anything without any plug-in.
That being said QuickTime is installed as part of iTunes so a lot of Windows users do have it.
But that being said other Windows systems, like Win98, can't install Quicktime.