If you can get some web pages but not all web pages then I would suggest you have a spyware or virus proble. Use the free AVG antivirus and spybot search and destroy and adaware to check for these. Also clean out the hosts file. On an xp machine it is c:\windows\system32\drivers\etc (it is hidden so you will have to ensure you see hidden files). Open hosts with notepad and ensure it only has 127.0.0.1 localhost in it (aside from the text preceded by #). You can also make it read-only.