: Ok, I seem to have created a problem inadvertently. My .m4a files(you
: probably know what types of files they are--if not, just go Something it)
: set in my hard drive were always programmed to play in Windows Media
: Player. I had used a codec in order to do so.

: Now for some reason(I believe it was either after an update or a deletion) my
: m4a's can't be played by anything. It's a blank thumbnail, no program icon
: to show as a default program, none of that. Pressing Enter does nothing,
: when I right-click on it and click Open with, no dialog box or anything
: shows up for me to choose the program to open it with. Going to the
: Default Programs feature, when I go to the m4a extension, the Default
: Program listed says Unknown Application. Nothing happens when I click
: Choose Program to switch it, again nothing happens.

: I tried restoring my computer to my least recent version, but for some reason
: it failed!

: What can I do?

: It's Windows 8, by the way.

You will need to re-associate the file type with whatever application can use it. Or, just install Arch Linux and you will never have this problem again.