Back to Black
Windows Movie Maker works their Timeline view so that no matter when and where you drag and drop a video clip into it the clip will then jump to either the beginning or the end of the last clip. If you try to create a clip gap in the Timeline the clips will just re-position themselves so that they are all back to back. There is no inherent way to create this gap in Windows Movie Maker, so if you want to create a space of black, otherwise known as a color solid, you have to go through an entirely different process.
Location, Location, Location
The easiest way to do any video generation in Windows Movie Maker is through its text function. First, identify the location in the Timeline where you want to put the black spot. This may be at the end of a series of clips, or even in between a few. Go ahead and select a clip that may be in front of or behind the location you want to put the black color solid.
Go to the left Windows Movie Maker Movie Tasks panel and choose “Make titles or credits” under the Edit Movie heading. Once it is open select the location option that is relative to the clip you have selected. This means that if you want to put it after a clip then select “Add title after the selected clip in the timeline.” Once you are here you are going to get a two level text box. Go to the top of this and put in a few blanks spaces with the space bar. Then go down below and choose “Change Title Font and Color.” Once you are here go under the Color heading and click the color box. This will take you to a multi-color series of boxes from which you can choose the color of the background. If you want to make it any random color solid, here is the place to choose it. To make it black you are going to have to create a custom color. Choose the Define Custom Colors button at the bottom of the window. Here you will be given a large rainbow box on the left and a slender white to black column on the right. Go to this and drag the color identifying arrow all the way down to the black, signifying that the color you are identifying is entirely and purely black. Once you have done this you then hit the Add to Custom Colors button below. Once it is in the Custom Colors section of the normal color selection boxes select it so that it is identified under Color in the normal Change Title Font and Color display. After the color is set just go ahead and click “Done, add title to movie” and it will appear in the Timeline in the location you indicated. Now that it is in the Timeline you can stretch or shorten the black color solid as much as you want.