Mac,
You are answering the wrong question - the question was "How can I block access to this range of IP addresses", not how can I manage name resolution.
The HOSTS file manages translation of host names into IP addresses, NOTHING ELSE!
It cannot be used to block access to IP addresses BECAUSE IF YOU KNOW THE IP ADDRESS IT IS NOT EVEN CONSULTED!!
With a proper firewall it is simple to write rules to block traffic to / from specific addresses or whole blocks of addresses as in this case; however, Windows isn't a firewall (understatement of the century), and most of the home WAP/Switch/Firewalls don't allow this level of customisation. I'm sure that there are some that allow this - I'm also sure that some of the software firewalls that run on Windows can do this.
I believe that you could write static routes into Windows networking via the command line, and it would be simple to put this into a script that runs whenever you boot, but with more than one device on the network, it makes more sense (and is easier) to put it on the firewall.
SD