Windows XP SP2 ADSL dialing is not available, prompting "restricted or connectionless"

A friend of a computer, Windows XP SP2, ADSL dial-up Internet, the original has been normal, this day suddenly can not surf the Internet. View the network connection prompt
Restricted or connectionless, run the ping 192.168.1.1-t command horn emits an alarm sound that has never been encountered before. began to suspect that the virus, killed half a day did not kill the other, and then installed a number of suspected software, replace the network card, cable, ADSL, etc. are invalid. Online enumeration of data, most said that the designated IP address can be, but this computer is still not online, only the network connection on the yellow exclamation point is not. According to the phenomenon, the hardware is not a problem, then the problem should be in the network protocol.
To Microsoft to find an article to the effect is:
After you install Windows XP Service Pack 2 on a computer that is connected to the Internet through a DSL modem or cable modem, you may receive a "Limited or no Connectivity" (restricted or connectionless) message
Symptoms
After you install Microsoft Windows XP Service Pack 2 on a computer that is connected to the Internet through a Digital subscriber line (DSL) modem or through a cable modem, you may receive a message similar to the following when you try to connect to the Internet ：
Limited or no connectivity:the connection has Limited or no connectivity. You are able to access the Internet or some network might.
You may also receive error message 678 or error message 769.
Reason
After the Point-to-Point Protocol (point-to-point over Ethernet, PPPoE) is created in Windows XP, Windows XP creates both local and broadband connections. Because Windows XP is designed to create two connections and requires automatic proprietary Internet Protocol Addressing (Automatic Private Internet Protocol Addressing, APIPA) addresses, Windows XP should not refer to Out of the local connection has restricted connectivity.

However, if your computer is not configured as a PPPoE client and the computer obtains an APIPA address, there is restricted connectivity in this case. Therefore, Windows XP should indicate that a local connection has restricted connectivity. For example, this problem may occur if there are no Dynamic Host Configuration Protocol (DHCP) servers available on your network.

You may also receive this message if one or more of the following conditions are true: 1. The DHCP server in the hard wired network is down. In a home network, this server can be a server for an Internet service provider, your personal router, or your DHCP provider.
2. The DHCP server in the wireless network is down. On a home network, the server can be the ISP's server, your personal router, or your DHCP provider.
3. In a wireless network, this message may be displayed when you use an incorrect Wired Equivalent Privacy (WEP) key or if you do not have a WEP key.
4. You may not have an IP address, or your TCP/IP settings may be corrupted.
5. You may experience other issues related to Internet connectivity.
Alternative methods
Sometimes, you may receive this message even if your computer is currently connected to the Internet. To disable the message, use the following procedure:
1. Click Start, click Run, type Ncpa.cpl, and then click OK.
2. Double-click Local Area Connection, and then select Properties.
3. On the General tab, click to clear the Notify me when this connection is restricted or not connected check box, click OK, and then click Close.
Note: This does not solve the problem. It just closes the message.
The above is true, but there is no solution to the problem. According to the phenomenon, the Winsock registration information should be corrupted causing the connection to be lost, XP SP2 added the command of Netsh winsock reset, which resets the Winsock directory to the default configuration. This command can be useful if you have installed an incorrect LSP that can cause network connections to be lost. Although you can restore a network connection by using this command, you should use caution because the previously installed LSP will require reinstallation. Whatever it was, the dead horse was treated as a live horse, and at the run the type:
"Netsh winsock reset" carriage return
Then reboot ... Everything's fine.
I wonder if this problem has something to do with the ISP. Because the telecom people come to say that you are routing the Internet, is your computer problem. And then to solve the problem, the routing function is canceled, but still can't surf the internet. Running Netsh winsock reset solves the problem. Indicates that the registration information for Winsock is corrupted. But who destroyed it.