Open Windows Movie Maker. On your desktop, click on the small circle with the Windows logo at the bottom left of the desktop. Select "All Programs" and scroll down to the folder labeled "Windows Live." Next, click on "Windows Live Movie Maker."
Find your video. At the top of the Windows Movie Maker screen, click on "Add Videos and Photos." On the left is a column of icons. Windows tends to save movies in a section entitled "Videos," which is labeled accordingly. Click on the "Videos" icon.
Import the video. A folder will open containing any videos saved there. Double click on the video and it will be loaded to Windows Movie Maker.
Click on the "Visual Effects" tab at the top of your screen. A row of icons will appear. On the far right, click on the "Brightness" button.
Adjust the brightness. After clicking the "Brightness" button, a small sliding bar will appear. Click on the bar, hold down the left mouse button and drag the marker to the right to increase brightness.
Save the movie. Click on the small icon at the top left of the screen with an upside down triangle next to it. Select "Save Movie" from the dropdown list and save it in your desired format, such as widescreen or high definition.