Bree said:
So you have photo gallery installed then? As I said, the two are a pair and will be installed (or uninstalled) together. I get the same 'this program is installed' as you, but then I do have (and use) Movie Maker. See if you can find its executable with File Explorer. Look for...

C:\Program Files (x86)\Windows Live\Photo Gallery\MovieMaker.exe
I expect MM is already installed - just start typing movie maker in the search box.