It looks like you either don’t have ImageMagick installed or, more likely, it’s not included in your system path. I just installed it on a new system, and it gives you the option to include it in the path during install. It’s checked by default.
It’s also odd that FFMPEG wasn’t included with your ImageMagick. Are you sure you’re running the right installer? On my Windows 8.1 64bit system I installed this build:
http://www.imagemagick.org/download/binaries/ImageMagick-6.8.9-8-Q16-x64-dll.exe
And it works great.