The most important thing to do before using large HOSTS  files is to disable the Domain Name Service client ("DNS Client" or "DnsCache") service on your machine. It sounds bizarre, but the DNS client isn't needed to do DNS. Worse, if you have a large HOSTS file (which is what I suggest), the DNS client chokes your entire PC. The DNS client acts as an intermediate step looking up (and remembering) internet names and addresses on your PC. If you disable the DNS client, you may need to let your firewall software know that individual applications are allowed to do DNS lookups. Other than that, no problems. Microsoft has an article that tells you how to disable DNS caching by the registry. They mention the services control panel as an easier way, but they don't tell beginners how to do it! Here's how to do it. 

You need to open up the "Services" configuration window. From the "Start" button, select "Run", and enter "services.msc". There are other ways to do this, of course (aren't there always?), but this is the simplest.

Scroll down the list to the "DNS Client" (shown highlighted here). Under the "Startup Type", it should show "Disabled". If it doesn't, double-click the entry to open it's "Properties" window.

Select "Disabled" from the list of choices for "Startup type".  If the "Stop" button isn't grayed out (it's grayed out in this picture), press the "Stop" button to stop the DNS Client service. Now you can install and use a really large