I have two almost identical machines, one desktop and one laptop, both bought and installed at the same time, both running XP Pro and Office 2007, both connected to the same Comcast router and cable Internet.
This afternoon, the desktop could not connect to the network. Outlook cannot retrieve email and none of the browsers (Firefox, Explorer, or Chrome) can access google.com or amazon.com. The laptop is not having any problems at all.
I have rebooted the cable router and the computer 2-3 times. I have checked all of the cat5 cables. The cat5 connection on the back of the computer shows a flickering light as always. If I unplug the cat5 cable from the router, I get an error message on the computer saying that the local area network cable is unplugged. When I plug it back in, it says the local area net is connected at 100.0 MPS, just as on the laptop, which is connected to the same router.
I ran the Explorer diagnostics. It reports a number of errors that I do not understand and it recommends that I contact my ISP. But I find that hard to believe since the laptop is working just fine.
I'd be happy to upload the Explorer diagnostic report if there is a safe place to do that. I don't know if it has any personal information or any information that a hacker could make use of.