I don't really understand what all the above does, why, etc etc. Anyway, at first I could see my web pages by typing http://localhost or selecting F12 from Dreamweaver. I didn't do any work on the website for a week or so, and when I came back all I can now get is the above message in Firefox. In IE, I get Page Cannot Be Displayed with 'Cannot find server or DNS Error' at the bottom of the page.
I've got XP/SP2 with ZoneAlarm [free version] and AVG antivirus, as well as a few antispyware products. The guy from the website company reckoned the problem was ZoneAlarm, but even with that deinstalled I got the same message. Ditto AVG.
He also reckoned it could be corrupt php installation, but reinstalling that did nothing. He's away from work for a while now and I can't find any solution to this on forums.
Can anyone PLEASE help?