IIRC the relative path works or not depending on whether you run Windows XP or Windows Vista.
I use statements like these in an autorun.inf on a USB Flash Drive.
You can consider the syntax an extension of the “open=” statement, with the possibility of having multiple entries:
shell c=Start TrueCrypt
It works in Windows XP but not in Windows Vista the last time I tried. I haven’t bothered investigating how to do it properly in Windows Vista yes.
Maybe this will help: