This may sound silly suggestion to even post on Windows Reference but will help avoid some annoyance with Windows Vista and Windows 7.
The host file is the one where one enters hostname and IP Address pair manually as against being served by a Name server (ex: DNS). As always the “host” file is under C:\windows\system32\drivers\etc\ or %systemroot%\system32\drivers\etc\ and hence cannot be edited by normal users.
To edit the host file,
Click Start – search for “Notepad“, right-click and select “Run as Administrator“. This should launch notepad with elevated privileges. Now, open the host file from the File menu, edit and save.