Why does my cable Internet connection frequently fail?

Jack McKee, Barrington, Illinois

First, update your security programs (antivirus, antispyware, firewall, and so on). Next, check for viruses and spyware. If a malicious program has turned your PC into a zombie, your Internet link may be overloaded with hidden, illegal activity. One infected PC can block access to your entire network.

After determining that your PC is free of malware, ping your connection to verify that the network hears you. Select Start, Run, type command /k ipconfig, and press <Enter>. The resulting box shows your network settings, one of which is your PC's IP address. At the command prompt below these, type ping ipaddress, where "ipaddress' is the number that follows "IP Address'. Press <Enter>. You'll see a series of replies along with a list of ping statistics in milliseconds (see Figure 1). If the ping fails ("Destination host unreachable"), the problem is with your PC's network adapter, or the connection between the PC and the router. Type exit and press <Enter> to close the window.

One possible fix is to restart the router, modem, or whatever device plugs first into the cable running from the wall. If the box lacks a power button, unplug it, wait a minute, plug it back in, reboot your PCs, and see if the problem is gone.

Another potential low-cost solution is to swap cables. Change the cables connecting your PCs to the network boxes one at a time to see whether a bad cable was responsible for the outages.

If all of the computers on the network lose Internet access simultaneously (and you've determined that malware isn't to blame), the problem is not with Windows, the PCs' hardware, your cables, or your Wi-Fi connection (if any). But if only one computer on the network loses access, the source of the problem could well be one of those components.

If you use a Wi-Fi network, check your wireless card's connection strength (most cards put an icon for this in the system tray). If the signal is weak, either remove obstructions (such as plants, fish tanks, or CD collections) from the signal path or move your PC closer to the wireless transmitter.

If all of your equipment is working, call your ISP's tech support. If your ISP didn't provide your cable modem or router, you may also have to call the product manufacturer's support line. (Browse for Michael Desmond's tips on dealing with tech support.)