I too installed Service Pack 3 downloaded from PC Authority, as I chickened out of the Complicated Microsoft one, over service Pack 2 with Internet Explorer 6, only because I need to Install Net Framework2 to run several Utilities. I couldnt connect to the Internet with my laptop at the Internet Cafe after, to do a connected download, and then had to do heaps or research only to find out that there were a lot of people in the same boat. This is how I solved my problem.
Dont just go to the Internet Explorer Menu TOOLS Internet Options Connection LAN settings Aitomatically detect settings to select this checkbox because there is more:
Go to My Netwok Places, right click Properties or Open Network Connections on the Toolbar. Both get you to the LAN or High Speed Internet settings, right click Properties, General. Scroll down and select Internet Protocol . Select the Properties Box, above the description below. On the General tab, Clear both the Use the following IP and DNS server address boxes , by selecting both Obtain an address Automaticaly. Select the Alternate Configuration tab, deleselect the User configured
and select Automatic private IP address . Go back to General Tab and Select the Advanced settings below.
On IP Settings tab, IP addresses, check if the DHCP shows as enabled, and Default Gateways Automatic metric box is ticked. On the WINS tab, enable Net BIOS to Default settings. OK all boxes to confirn and exit. There are lots of other settings and some of these above may already be enabled. No need to it in exactly this order but it is easier to follow. Sorry I couldnt attach pictures.
It is easy to overlook these simple settings as I did. If this doesnt help you it may help many others.