My main machine had a hardware issue, so I'm trying Windows 8.1 Enterprise in another machine. When I install my HOSTS file, all browsers (Firefox, Chrome, Opera, Explorer, SeaMonkey) begin to use between 96% and 100% of the CPU. Tor, for obvious reasons, is the only exception. The problem disappear when I revert to the default (empty) HOSTS file. The DNS Client service is disabled as it should be when a large HOSTS file is used. Changing all entries from 127.0.0.1 to 0.0.0.0 does not work. I never had this problem (or any other problem whatsoever) with my HOSTS file while I was using previous Windows versions. Please note that I'm not wanting to start a discussion about the pertinence of using a HOSTS file. I just want to keep using my HOSTS file (as I always did) in Windows 8.1 Enterprise. Any help will be appreciated. EDIT: I'm not using Windows Defender.