delete it. windows will generate another one. the host file is where you can map an ip to a particular domain. so if i had www.cnn.com linked to abc's ip then whenever i enter cnn.com it will take me to abc's site. If the ip is old/outdated then you get a page not found.
Try disabling your firewall and see if you can access those sites or not afterwards.
EP, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS