you want to know which command are you running on command line? download which here (at the bottom of the page).
The standard way to resolve that is to find the hosts filerun a program as administrator: CTRL+SHIFT+ENTER over its icon
and map your loopback address ( 127.0.0.1 ) to "localhost".
There's an issue connected to doing that on Vista.
The hosts file is considered a system file by Vista.
You have to first take ownership of it then grant yourself full control.
These are the two commands that you need to run from an elevated command prompt.
(Right click "command prompt" and choose "Run as Administrator") :
takeown /f c:\windows\system32\drivers\etc\hosts
icacls c:\windows\system32\drivers\etc\hosts /grant yourusername:f
If you installed to a drive other than "c:", modify accordingly, of course.
Now you can open the file with notepad, insert this line and save the hosts file
( make sure it doesn't acquire a .txt extension ) :
If that doesn't fix it, you have a bad install of the TCP/IP stack.