The most easy way that I can think of is by using window movie maker. Follow the instruction below.

1.Open Movie Maker

2.Change the storyboard setting to time line . (Its located at the bottom left corner of the screen, right next to the zoom buttons.)

3.Click the prefered video clip and drage it to the place where it says Audio/Music.

4.Go to file menu and click Publish Movie.

5.Click next. Select the drive where you want to save and click next again.

6.When you come across Choose Settings, click the best according to the need. If you want the high quality audio, click More Settings and brouse accordingly.(Higher the Kbps, better the quality)

7.Click Publish.

To extract the Video only , drag the video to the place where it says video. Then click to the "+" sign next to the video. Then you will see transection and audio appearing. Rt click to the audio portion and click at the place where it says Mute. Then go to the file menu and click pubilsh movie. Follow the instructions.

I guess this might help you. Its pretty easy to do and you dont have to download anything.

Hope you find this helpful.

Good luck