I didn't also get the "ln -s /opt/video.avi" link to work, so i made folder "/opt/media/" and put the startup video there. Then in mc went to "usr/share/hildon-welcome/" and i deleted the "media" folder and all is left to do is link the "/opt/media" to "usr/share/hildon-welcome". Thats how i got it to work, i did all this from mc. Hope this helps.

While i did this i also optified my sounds folder and some other stuff and gained extra 10mb of space in root