Windows XP SP2 ADSL dial-up cannot access the Internet, prompting "restricted or no connection"

A friend's computer, Windows XP SP2, ADSL dial-up Internet access, has been normal, and suddenly cannot access the Internet on this day. View the network connection prompt"
Restricted or Not connected, run the "ping 192.168.1.1-t" command to generate an alarm, which has never been encountered before. I began to suspect that the virus had not been killed for half a day. I had to install some suspicious software, replace the NIC, connect lines, adsl, and so on. Most of the information on the Internet can be found after an IP address is specified. However, this computer still cannot access the Internet, but only the yellow exclamation point on the network connection is absent. According to the phenomenon, there is no problem with the hardware. Then the problem should be caused by the network protocol.
I found an article at Microsoft to the effect:
After Windows XP Service Pack 2 is installed on a computer connected to the Internet through a DSL modem or cable modem, you may receive a message "Limited or no connectivity" (restricted or connectionless)
Symptom
After Microsoft Windows XP Service Pack 2 is installed on a computer connected to the Internet through a digital subscriber line (DSL) modem or a cable modem, when you try to connect to the Internet, you may receive messages similar to the following:
Limited or no connectivity: The connection has limited or no connectivity. You might not be able to access the Internet or some network resources.
You may also receive error 678 or error 769.
Cause
After you create a point-to-point over Ethernet (pppoe) connection on Windows XP, Windows XP creates both a local connection and a broadband connection. Because Windows XP is designed to create two connections and requires an automatic private Internet Protocol addressing (apipa) Address, Windows XP should not point out that local connections have restricted connectivity.

However, if your computer is not configured as a pppoe client and the computer obtains the apipa address, restricted connectivity exists in this case. Therefore, Windows XP should point out that local connections have restricted connectivity. For example, if no Dynamic Host Configuration Protocol (DHCP) server is available in your network, this problem may occur.

This message may also be received if one or more of the following conditions exist: 1. the DHCP server in the hard-wired network is stopped. In a home network, this server can be an Internet service provider's server, your personal router, or your DHCP provider.
2. the DHCP server in the wireless network is down. In a home network, this server can be an ISP Server, your personal router, or your DHCP provider.
3. In wireless networks, this message may be displayed when you use an incorrect wired peer-to-peer (WEP) Key or do not have a WEP Key.
4. You may not have an IP address, or your TCP/IP Settings may be damaged.
5. You may encounter other problems related to Internet connections.
Alternative Method
Sometimes, even if your computer is connected to the Internet, you may receive the message. To disable a message, follow these steps:
1. Click Start, click Run, type NCPA. CPL, and click OK ".
2. Double-click "Local Connection" and click "properties ".
3. On the "General" tab, click to clear the "notify me when this connection is restricted or there is no connection" check box, click "OK", and then click "close ".
Note: this does not solve the problem. It only closes the message.
The above is true, but there is no solution to the problem. It is determined that the winsock registration information is damaged, resulting in connection loss. XP SP2 adds the netsh winsock reset command, which resets the Winsock directory to the default configuration. This command is useful if an incorrect LSP is installed that may cause network connection loss. Although you can use this command to restore the network connection, you should use it with caution, because previously installed LSP will need to be re-installed. Regardless of it, the dead horse is treated as a live horse doctor and is running the following type:
"Netsh winsock reset" Press ENTER
Then restart ...... everything is normal.
I wonder if this question has something to do with ISP? Because when Telecom people come, they say that you are a route-based Internet connection, which is a problem with your computer. But I still cannot access the Internet. After running netsh winsock reset, the problem is solved. This indicates that the winsock registration information is damaged. But who destroyed it?