This is a known XP SP2 bug. There are several scenarios responsible for this. However, since you are unable to connect to the Internet, we can rule a couple of them out. Try the following:
1. Turn off your system and unplug the power to your DSL or cable modem to allow them to reset.
2. If that alone doesn't work, check to see if they have a reset button on the back. Repeat the above step and try the reset button.
3. Go to a command prompt and type
netsh winsock reset.
4. Go to the command prompt and type
ipconfig /release, hit enter then type
ipconfig /renew.
5. When you are able, download the MS
patch.