I have a Humax fvp5000t but I hope this should work for older models too.
You've Copied or Moved a programme to your USB stick or Hard Drive and some time later you'd like to watch it again with the Subtitles still intact ... do this:
1) Make sure the programme files are in THE EXACT SAME FOLDER on your USB stick or Hard Drive that they originally appeared in after the initial Copy or Move from your Humax;
2) This means that when you plug in to the Humax the programme title will appear in your RECORDED PROGRAMMES LIBRARY list;
3) Play the programme from the RECORDED PROGRAMMES LIBRARY list and the Subtitles will reappear in the original broadcast format - big, colourful and on a black background.