First off, I would like to apologise if the solution to my problem is rather obvious, which is probably the case. 
I recently instaled AE CS6 and have been unable to even begin to learn the program because I can not get any type of video file to play. I read about codec issues, so I tried different formats (avi, mp4, etc), but I have had no such luck with any of them. And no, I don't have K-Lite installed, BTW. The only thing I can think of that might be installed on my computer that could possibly cause a codec issue would be my GOM player if it installs codecs automatically? But I only installed the default player.
Anyway, this is what I'm looking at: I import a video file and I can hear the audio, but I see nothing. Then, if I export it, I can see the finished video (in my GOM player) but there is now no audio!
I am stuck. S.O.S. please send help.
In case it helps, I am running Windows 8 with a dedicated NVidia video card, 16 GB of RAM, and a quadcore processor.
Any feedback would be much appreciated.