Sometimes you have to match the images with the sound manually, especially if you're creating the video by yourself or using a custom audio track for the images that are loaded into the application.
Secondly, a delay between video and audio could be caused by the codecs installed in your computer. I strongly suggest getting the Combined Community Codec Pack. It's excellent for both decoding and encoding.
After installing the pack, reboot the PC and then attempt to play the video file once more and you'll see that it plays normally.
