I have downloaded a movie...I am using nero to play is however...there is no sound...is it the way I download it? 
No, the way a file is downloaded doesn’t matter. To solve your problem you need to download and install the K-Lite Mega Codec Pack http://www.codecpackguide.com/ and then use Media Player Classic to play the file.
thanks for your reply..I have downloaded the codec but I’m not sure how to use the media classic with this...could you please inform this remedial learner step by step please...thanks so much!
From the same link download and install AC3 filter and try to play the file again.VLC, BSplayer and Media Classic are very good players and use their codecs.All are freeware so is good to have them on your computer. Here is a mirror of the same site: http://www.free-codecs.com/
thanks so much...works great now...