   fix my dad's computer
  When using IE on  my dad's computer, you keep getting 404's, but if you try enough times it will connect to the site.  Also, there are no favorites, not even the 'links' folder which you can't delete.  When you start up IE you get a dialog box asking which user you want to run it on.  One time the dialog did not appear, and his favorites showed up.The title bar in IE says "[page title] - Microsoft Internet Explorer provided by AT&T Road Runner."  (AT&T Road Runner is our ISP).  Thinking that the ISP put some foul settings into IE, I installed firefox, but with my intelligence, I imported the IE settings.  The favorites show up in firefox, but you get a message box saying the page couldn't be displayed quite often.The weird thing is, I had the 404 problem for one day only.I asked my dad how he got the dialog box asking which user to run IE on to show up.  He said it started doing that when he made an account for my mom.   
  Do you automatically obtain the DNS IP's from your ISP or do you manually set them? If you are provided an alternative DNS then have you tried making that your primary DNS? The sudden and intermittent 404's sounds like the primary DNS could be flaking out.   ;  Try getting an IP of an offending site (any site, it seems like), and connecting by using http://ip.ip.ip.ip ... if this doens't work, I have no idea- if it does, it's likely DNS not updating itself.   