i decided to switch to ubuntu, at last. and i’m definitely happy for the choice: smooth looking feel, decent speed and big selection of applications.
just one “down” point: i spent a whole weekend to install it! not bad, for a distribution said to be “easy on”… after an afternoon reading here, not finding any useful suggestion for my case, i found the solution.
for me (and my dell inspiron 5150) the alternate cd worked. so, just forget the install/live cd and go for the alternate: there are no differences, a part from the fact that you’ll have to forget the graphical istaller.