I'm using a Motorola Droid 4 and I cannot open AU files that I have copied to my SD card. I have installed both the Free Doubletwist player and I bought the WavPlayer app. Both of which are supposed to open AU files. Instead when I browse the SD card contents using My Files and look at the .au file, the first icon is a ?. I went into the apps and there is no file-open or anything and there is no Open-with type of option in My Files so I can't figure out how to open the AU file in one of the players. Is there a file association tool that should set this for me?