Support for Windows Vista without any service packs installed ended on April 13, 2010. To continue receiving security updates for Windows, make sure you're running Windows Vista with Service Pack 2 (SP2). For more information, refer to this Microsoft web page: Support is ending for some versions of Windows
When you try to change the Hosts file or the Lmhosts file in Microsoft Windows Vista, or Windows 7, you may receive an error message that resembles either of the following.
Error message 1
Access to C:\Windows\System32\drivers\etc\ hosts was denied
Error message 2
Cannot create the C:\Windows\System32\drivers\etc\hosts file. Make sure that the path and file name are correct.
This issue occurs even though you log on by using an account that has administrative credentials.
To work around this issue, follow these steps:
Click Start, click All Programs, click Accessories, right-click Notepad, and then click Run as administrator.
If you are prompted for an administrator password or for a confirmation, type the password, or click Allow or Yes.
Open the Hosts file or the Lmhosts file, make the necessary changes, and then click Save on the Edit menu. If using Windows 7, you will need to click Save on the File menu.