Set up the screen capture deviceInstall Screen Capture Recorder and configure by selecting the shortcut "configure by resizing a transparent window". Start broadcasting the desktop by choosing the shortcut "stream desktop local LAN", and "Start Normal 10 fps".
Capture the screenInstall 32-bit ffmpeg (even on 64-bit Windows) and capture as follows (press "q" to stop):
ffmpeg -f dshow -i video=screen-capture-recorder -r 10 -y recording.mp4
Convert to the target formatFor example, convert to .wmv and retain just the first 60 seconds (see "-ss" for skipping the start and "-q:v 10" to control the size/quality):
ffmpeg -i recording.mp4 -t 60 -b:v 1000k -vcodec wmv2 myfile.wmv