Video and Audio Out Of Sync?

I have the Nikon l820 and whenever I transfer a video from the camera to my laptop, about half way though the video, the audio goes out of sync.
Does anyone know how to fix this?

Yes, get a better computer. The problem is the buffer in the computer can't keep pace with real time codec conversion when downloading. There's nothing wrong with the source file from the Nikon. Most likely if you play the file off you hard drive it will be fine. If not, then you really need to invest in a new computer.