Problem after installing Win XP SP3

Im operating a computer classroom. We have 3 classrooms and 20 PCs in each of them. They are being updated now to SP3. Almost everything worked out fine...but 5 computers have now problem connecting to the internet. LAN is working perfectly... I can connect to the others computers in the classroom and to different network places but not to the internet... I have treid uninstalling SP3... uninstalling the LAN card and reinstalling it...checked the network parameters...almost everything... any suggestions?

 

Sometimes, if your running a firewall other than XP's own firewall, the XP firewall gets turned on by the SP3 installation. When this happens the two firewalls collide and often you lose connectivity. So if your machines have a third party firewall check to see if windows firewall is on too, and turn it off (Start > Control Panel > Windows Firewall).

If thats not the case try this:
Go to Start > Run and type CMD and hit enter
at the prompt type "ipconfig /flushdns" without the quotes noting the space after fig
hit enter and at the next prompt type "ipconfig /renew"

This will flush out your ip configuration and rewrite it from scratch and can often kick start a PC's networking.

 

Lastly you can turn off your router and modem (or unplug) then turn off all the PC's in the room (including the ones that work) and leave them off for 30 seconds. Then start up all the PC's and let them finish loading completely. Then with all PC's on, plugin the router and then the modem (this is called power cycling the router/modem). If any of the PC's show the "Found New Network" window set them to Trusted and hit OK. If its still not working try going to each PC in turn and running the network setup wizard, making sure each unit has the same workgroup name.