Launch Windows Movie Maker. Select the "File" button in the upper left corner. Select "Open" and locate the video file you would like to edit on your hard drive.
Click and hold the mouse button to drag the file into the time line at the bottom of the screen. Highlight the clip so it appears in the right-hand corner, above the time line. Select "Play" to preview it to determine which part you would like to cut.
Wait until the blue time line cursor is over the appropriate place in the video. Mouse over the blue line until a double-ended red arrow appears. Click and drag to the left to cut the end of the clip. Likewise, click and drag to the right to cut the beginning of the clip.
Select "File" and "Save" to save your new clip. Ensure you give it a new name if you don't want to lose the original video.