it's under the system directory:
- %systemroot%\hosts (95/98/Me)
- %systemroot%\system32\drivers\etc\hosts (NT/2K/XP)
if there are any entries other than 'localhost', delete those lines, and save it.
127.0.0.1 localhost
and don't forget perform this command after modification:
attrib +R %systemroot%\system32\drivers\etc\hosts