To install MEncoder on windows server to make it work with AttachMax, please follow steps below:
1. Download FFmpeg for windows from http://www.attachmax.com/MEncoder_for_Windows.html (9.85MB).
2. Unzip it to some directory (e.g. C:\Program Files\mplayer).
3. Open "Servers" tab in AttachMax admin panel and insert MEncoder path (e.g. C:\Program Files\mplayer\mencoder.exe) and MPlayer path (e.g. C:\Program Files\mplayer\mplayer.exe).

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

FFmpeg for Windows works faster, than MEncoder from our experience.