Step 1: Step 1
Again, this method only applies to PCs.
The first thing you are going to need to do is open up Notepad (if you don't know what that is, search for it in the start menu. It's for coding things, or otherwise known as magically making things happen with weird letters). Don't worry, it's nothing complicated. Like, at all. Honest.
Notepad will need to be run as the administrator for this step to function correctly.
If you're not the administrator of the computer, right click Notepad and choose "run as administrator". Click "Ok" if prompted.
If this fails, ask whoever's the administrator of your household to go on their account and let you do this.
If that fails too, forget the whole thing. Sorry. :P
Anyhow, copy and paste the following into notepad, and leave it open for now:
<Transition name="Bluescreen" iconid="12" comment="Makes first clip show through blue areas of second clip">
<Param name="KeyType" value="1" />
<Param name="Similarity" value="100" />
<Param name="Progress" value="0.0" />
Step 2: Step 2
Name the file "Bluescreen.XML" and save it in this location:
Program Files > Movie Maker > Shared > AddOnTFX
If you don't see a folder named AddOnTFX, make a new folder with that name inside the Shared folder.