How to change the format of a video?

I want to edit a video in windows movie maker. I use a Nikon Coolpix L11 to record these videos. Whenever i try to upload them into windows movie maker, it just says it cant work because the format isn't right, so i go to a website to change the format, and i do, and i save it. I change it to the right format for windows movie maker, whenever i try to put it into windows movie maker it says this:

The required codec was not downloaded automatically because the Download codecs automatically check box is not selected in the Options dialog box..

HELP! WHAT AM I DOING WRONG?How to change the format of a video?
wmm is not a very reliable program. What you are experiencing is a very common problem amongst users.



You can try the K-lite codec pack or get yourself another reliable video editing program.