This is also an important thing in video editing. And this is a basic thing. Let's do it with Windows Movie Maker. There are also two main ways to do this with Windows Movie Maker by the splitting method and the trimming method. First of all open Windows Movie Maker and import some video clips to it.
Now we are looking the first way. So add the imported video file to the Timeline. Get the cursor near to one end of the video clip on the Time line. You can see the cursor in different icon. So click it and drag trim inside. And it will trim your video clip. But your video cannot expand outside of your video. If your video has trimmed and it can be expand as same way to the outside up to its original length. And you are finish with trimming.
The second way is by splitting method. So first add the video clip on to the Timeline. Then select the video clip on Timeline and adjust the indicator to the place you want to split. After that click on the split button or press ctrl+L.Left hand side picture shows the indicator on the Timeline and splitting button. Like that you can remove unwanted parts from your video.
