Windows 95/98/Me c:windowshosts
Windows NT/2000/XP Pro c:winntsystem32driversetchosts
Windows XP Home c:windowssystem32driversetchosts
Windows Vista,7 c:windowssystem32driversetchosts

It doesn’t have an extension.

Modifying requires admin access on NT/2000/XP and greater.

Notepad must be started with full admin privileges by Right Clicking and saying “Run as Admin.”