In Video Edit Magic, you can replace the background color with a different color by using the Chroma Key Color effect. First, create a Video Color Clip to fill the screen with white. To do this, click Edit >> Add Text As >> Closing Credit. This will add a video color clip, to Video Track 1 and a Text Effect to Effect Track 1. Delete the Text Effect. Right-click on the Video Color Clip and set its color to White.

Put the video with the black background on Video Track 2, and the Video Color Clip on Track 1, starting in the same place. Use the mouse to adjust the Color Clip's length so that it is the same as the video clip.

Now, add a Chroma Key Color transition effect to the Timeline. Click on the black square under Primary Colors, to make black areas in the video transparent. The white color will show through, replacing the background with white in the Preview window. You may have to adjust the Similarity setting to make the appearance perfect.

We have published an article on using the Green Screen or Chroma Key Color effect: https://deskshare.com/resources/articles/vem_greenscreentechnique.aspx.