For me I'd try a Live Linux OS (no install, no learning linux) and see if the content plays in the Linux OS. If it does then make it a warranty issue. You didn't tell how old this PC is but such trouble on a new machine is definitely a warranty issue. Be sure to have full backups of your stuff because my bet is they'll start with a factory reset.
I have sound issue on all kinds of media players.
1) On GOM, BS, and WMP video (MP4, avi) runs for a couple of seconds with no sound during that period.
2) VLC runs the videos all right but still no sound.
3) I cannot play music (mp3) on Itunes, Spotify, GOM, WinAmp. It doesn't even start and on Spotify, it just skips to the next song continuosly without playing any of them.
I'm using Windows 8 HP laptop. I tried rebooting several times and couple of solutions which didn't work. (Downloading CODECs, changing directory name on VLC , running CDM as admin and running SCANNOW command.)