Hang on ... I think we are crossing what we are thinking of.
When you plug the pendrive into Ubuntu you are saying it automatically mounts but then you have to double click whatever is in it to launch? (is this right)
Assuming it is, I can tell you that the autorun.inf (as far as I know) will do nothing in Linux. I am guessing you want something like putting in a music CD
and your player automatically detects it and starts playing?
I may have to leave this to someone else as not sure, but I hope my extra information will aide in someone helping you