You still haven't answered what version you installed. If you are using the older ones, it might not work properly on Windows 8.1
If you're serious about paying for support, why not buy a real editor (or even just have a monthly license)? Adobe CC's video editor is available for ~$20/mo ($50/mo for everything), and editors from Sony Vegas to offerings from Roxio and Pinnacle are fairly cheap.
If you aren't willing to part with money, you can always use Blender's editor, it's not a drag and drop friendly application, but it will certainly do anything movie maker can, and much more too.