I don't think any program can convert SMIL files to DVD (unless .SMI or .SMIL files are actually Real Media/Audio/Video files).

Can you play your presentation with a Real Player? If your Real Media audio files play fine and you can see the slides perfectly by playing .SMI files, then screen capture software will be the best solution. If you can't play the presentation, but can watch it online, then again use screen video capture software to record into MPEG-2 format and burn your recordings to DVD.