No forced subtitles when converting from avi to DVD

Hi guys,

What I want to do - I have an .avi with two subtitle files, .idx and .sub. I want to create a DVD playable on regular home DVD player, with forced subtitles. The avi plays fine and forced subtitles are visable using WMP and MediaPortal

Here's my problem - I cannot create a DVD that displays the forced subtitles.

What i have tried so far - I have converted the idx and sub files to .srt. I have tried muxing the .avi and .srt using SubMux. I have tried VirtualDub to add the subtitles to the avi which are visable when played in VirtualDub. I have tried AVI2DVD to convert the avi together with the .srt to DVD but no subtitles appear, when played back.

Do you guys have any other suggestions?

Much appreciated