There are a few "tricks" to get internet connectivity working again, even if you don't know the cause. Stop doing more tricks when connectivity comes back.
1) WinsockXPFix:
|MG| Free Download - WinSock XP Fix 1.2
Test for connectivity.
2) Uninstall the Network Adapter driver - XP will reinstall it on the next startup:
Control Panel > System > Advanced > Hardware tab > Device Manager button
Click the plus sign to the left of Network Adapters.
Right-click on the adapter you are having trouble with and select Uninstall.
Shut the PC down.
Turn off power to your router and modem in either order.
Wait 1 minute...
Turn modem power back on.
Wait 1 minute.
Turn the router power back on.
Wait 1 minute...
Restart the PC. Test for connectivity.
3) WinsockReset.bat
Open Notepad and cut & paste in the commands btween the lines:
-----------------------------------------------------------
netsh winsock reset catalog
pause
netsh int reset all
pause
ipconfig /flushdns
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Save this to a file named,say, WinsockRest.bat
In Explorer double-click this file name.
Test for connectivity.
4) I have another fix, but I need to figure out
how to upload the file in this board!