Hi Simon
The HOSTS file is protected by WIndows, for obvious reasons.
Sometimes a firewall/virus checker will also attempt to stop you modifying the HOSTS file.
It sounds to me like your Firewall/Anti Virus app is probably causing this issue.
Normally it is possible to tell said app to stop being over protective of the HOSTS file. Can you try and stop your FW/AV from attempting to protect this file. Most AV's have a stop protecting this file for 30 minutes type option.
It would also be useful in the furture if you start a question with the answers to this
Sticky Post
READ (and answer) BEFORE YOU ASK A QUESTIONThese posts can also be useful
WAMPServer 3 All you need to knowand this one
TROUBLESHOOTING TIPS---------------------------------------------------------------------------------------------
(Windows 10 Pro 64bit) (Wampserver 3.3.4 64bit) Aestan Tray Menu 3.2.5.4
<Apache versions MULTIPE> <PHP versions MULTIPLE> <MySQL Versions MULTIPLE>
<MariaDB versions MULTIPLE> <phpMyAdmin versions MULTIPLE> <MySQL Workbench 8.0.23>Read The Manuals Apache --
MySQL --
PHP --
phpMyAdminGet your Apache/MySQL/mariaDB/PHP ADDONs here from the
WAMPServer alternate Repo-X-X-X-
Backup your databases regularly Here is How dont regret it later! Yes even when developing -X-X-X-