Restoring the hosts file
Now that you know where the hosts file is or is supposed to be, you'll want to double check if it is there or if there is some form of back up there. If you find a file that looks like a backup of your hosts file, then copy that file to a file called "hosts". If you aren't sure, then don't. Note that the "hosts" file has no extension, so make sure this is the case. The hosts file backup (if any) is a basically text file (as is the original "hosts" file). It may be called hosts.bak or something similar. All you need to open and read it is the Windows Notepad program.
If you can't find the hosts file and a backup doesn't exist, then you'll have to create a new "hosts" file. To create one, you'll need to open the Windows Notepad program and enter the following information in it:
The "1" in the "127.0.0.1" must be at the very first column of the line. Also, there must be at least one space between "127.0.0.1" and "localhost". The second line is an IPv6 address mapping to localhost, and this line is part of the default hosts file for Windows Vista and Windows 7. There must be at least a space between "::1" and "localhost".
In Windows 2000 or XP, all you need to do to save this file as "hosts" and you are done. In Windows Vista or 7, you must have started the notepad program "as Administrator". This will allow you to save to the "hosts" file and the path where you are trying to save is a system type file.
Once you've created the new hosts file, you are done and you've basically recovered. If you had some IP address-name mappings in the original hosts file for your computers in your home network, then you may append them to the hosts file; each mapping must have its own line.
IMPORTANT: The hosts file typically doesn't disappear on its own. There should be nothing touching that file, unless you explicitly decided to modify it or you have a computer security program that modifies it to prevent you from going to malicious web sites. Thus, you should do a full system virus/malware scan as your computer may be infected! Just do this as a precaution.