I tried to edit the 'hosts' file in 'system32\drivers\etc\' folder, but windows says :This file is set to read-only. How can I edit and save the 'hosts'-file?

As the file is Read-only, right-click it, click Properties and remove the check mark. Make a backup copy of it, then using Notepad change its contents and save it (not as a .txt file, i.e. it has no extension). If you are unable to access the file, browse the Windows folder, right-click notepad.exe and choose Run as Administrator, then open Hosts.

Open an administrative command prompt (right-click and select "Run as Administrator"). Navigate to \Windows\system32\drivers\etc. Type: Notepad hosts. Since Notepad was invoked via the administrative command prompt, Notepad will run under the local Administrative token allowing you to edit the hosts file as necessary.

Dose not work for me at all. I run note pad as administrator - still get access denied. I can not change ownership or permissions of the file or the folder, even when antivirus is turned off. Even running in safe mode did not help.