If you are reading this, I'm going to assume you've upgraded or purchased at least one PC with Windows 7 or 8 and discovered Windows Movie Maker is no where to be found. In its place, Microsoft now offers a set of programs called "Windows Essentials". Often these programs are installed on a new PC but otherwise you must download the Movie Maker program to once again have the ability to edit movies.
Many people have tried the newer version of Movie Maker 2011 or 2012 and complained about the lack of a traditional timeline, issues with crashing, long times to prepare video files and the inability to customize the transitions, effects and titles. If you have been building up a library of custom titles, transitions and effects under Windows Movie Maker 6.0, none of these can be used in the newest Movie Maker because the rendering architecture has changed and Microsoft has no API for customizing things.
The good news is you can still use the latest version of Windows Movie Maker 6.0 from Vista. You can do this manually by copying the files from a Vista machine, registering some DLLs and creating a shortcut in your start menu. Or you can just use the installers I created below:
Movie Maker 6.0 for Windows 7/8 (64-bit) download here
Movie Maker 6.0 for Windows 7/8 (32-bit) download here
There are two versions (64-bit or 32-bit) depending on the version of Windows 7/8 you are running. If you are unsure, go to your 'Start' menu, right-click on 'Computer' and choose 'Properties'. System type should show 64-bit or 32-bit operating system. Pick the installer that matches. After that, don't forget to start previewing all the cool add-ons that you can have with this version.