Originally Posted by ramasaig
If you go to windows explorer, to the c:\windows\system32\drivers\etc\hosts file, right click, properties, security and sharing and then in the security tab somewhere -not sure because I'm not on a windows machine now but linux- is an option to change the owner of the file. Change the owner to your own username, save the changes, and after that you can just open and save that file as you please without windows ever whining about permissions again.
Alternatively you can start notepad as real admin (right click on notepad in the start menu and "Run as administrator") and then you should be able to save to. This is not needed if you applied the first trick.