How to voice over video?

I filmed a video with my Nikon d5100 with no talking. Then I filmed another with me talking. How can I show the video of me not talking, but hear the video of me talking? Any free video editor i can get? I use windows live movie maker, but I'm guessing that won't work. Any help?

Added (1). Check cable? Wtf?

Added (2). No, I already recorded this and i ain't doing it again. Just tell me how!

Check cable

You can put the video on a computer, and then record your voice over it. You can try looking on the internet for some more help.

Put your talking video on timeline and delete video but retain audio. You should be able to do this. Do a save as. New project - Put non talking video on time line and import the saved audio to the audio track. Then you will have to work out how you sincronise the end product.