Video screw-up on Windows 8

I recently got a new computer that runs on Windows 8. My computer will not play my movies, or rather, the movies play and the audio is out of sync with the video or the audio quality is scratchy. I've been looking at the posts on here, but they all seem to be geared towards XP or windows 7. What do I do? I've redownloaded iTunes three or four times and I tried some of the solutions that people posted for the older model computers, I even redownloaded all of my movies, but that didn't work either. Of course apple won't answer my questions over the phone. If anyone else has had this problem please please please tell me how to fix it, because I am completely out of ideas.