To install FFmpeg on windows server to make it work with AttachMax, please follow steps below:
1. Download FFmpeg for windows from http://www.attachmax.com/FFmpeg_for_Windows__1.html (5.7MB).
2. Unzip it to some directory (e.g. C:\Program Files\ffmpeg).
3. Open "Servers" tab in AttachMax admin panel and insert FFmpeg path (e.g. C:\Program Files\ffmpeg\ffmpeg.exe).

To use FFmpeg for flv encoding and thumbnails creation, you should select "ffmpeg" as "Video Tool" from "Config" tab in AttachMax admin panel.