I’m an Administrator on my installation of Windows 7 and had to edit the hosts file for one of my projects. I wasn’t able to make the changes though because it kept saying file was in use. I realized that I need to run notepad as the administrator and then I could make my changes!

1. I went to the start menu, and typed in notepad.
2. Right clicked on the notepad icon and selected Run As Administrator
3. Clicked yes when it confirmed whether it should
4. Navigationed to c:WindowsSystem32driversetchosts

Hope this helps!