A thumbs up for Winsockfix
Over the holiday, and because I could spell PC, I ended up being pointed at my brother in laws pc which was 'running badly'. To cut a long story short, they had been running on a broadband connection with no firewall or virus protection. They had collected 48 virus's and more than 400 pieces of spyware. Anyway, I cleaned out the virus's and the spyware only to find that the machine could connect to the internet and could ping an IP address but not a URL. I came to the conclusion it had a corrupted registry caused by spyware removal which left a winsock error.
I searched the internet and found a free utility called WINSOCKFIX which I downloaded onto my machine and ran on the corrupt system. It did the job a treat.
I have no connection with the makers of this utility other than being very satisfied. If anyone sees the symptoms described above, this could be a good starting point