This is not so good news about Revit 2012.... Appearently, it is not going to be as easy as it used to be to Activate or Re-Activate your Revit... So, all those 3GB install packages you downloaded and the unpackaged 6GB files... SAVE THEM! Or else you may be re-downloading them quite a bit.
Click here to see Revit Clinic's post about this unfortunate set-back in Revit 2012...
This could apply to us students running Revit on a 30 dayt trial... We MAY have to reinstall in order to activate our student licenses... so, again, SAVE THE INSTALLERS!