We had one of our WIN 7 LAPTOPS only make to the 20% download point and stopped there. This was the DRIVERS section... Finally had to reset the WIN 7 back to its original SAVE POINT. Then things went ok after that... Ours took around two hours as I recall to complete a 100% install time...
I also was using FIREFOX...
My second WIN7 Laptop went through the process without issues... My two WIN8 Laptops both had no issues... My two older DELL M90's WIN XP PRO are still laughing at me... I'm still running them however for my Ham Radio operations...
Roy Ken