I believe the install.inf file should delete itself (or be deleted by the car) after the update completes - I have noticed a few times that this does not happen, if you plug it back in your computer and delete it manually, then back into fiat, it will be fine.
Just out of interest; how often does the eco:drive software get updated?
I have only recently started using eco:Drive (as a recent owner of a 500 (which I love)) and it does seem to tell me there is an update almost everytime I plug it back into my computer to download the data to see what my latest eco:Score is??