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Diagnostic Tools

Each diagnostic tool described in this section serves to test the operation of one or more of the categories mentioned in the preceding section. The tools are discussed in roughly the order you should try them.

Some tools can be used to find problems in any of the many networking components. These tools quickly identify many problems.

The Network Window

You might not think of the Network window as a diagnostic tool, but it can be one. It will quickly tell you whether your computer's network discovery and file sharing features are turned on and whether your computer can communicate with any other computers on your LAN using Windows's file and printer sharing client services. If at least one other computer is visible and online, you can be pretty sure that your computer's network card and cabling are okay.

To use it, click Start, Network. The window that appears should look something like Figure 24.1, except that the names of the computers on your network will be different. My network also includes a router device, which also appears in this display because its Universal Plug and Play (UPnP) feature has been enabled.

Figure 24.1

Figure 24.1 The Network window shows whether your computer is communicating with other computers.

If you see at least one other computer besides your own displayed here, your computer's network cabling, network adapter, and drivers are working correctly.

An informational bar just above the list of icons may provide additional information about possible limitations to Windows networking. The bar is present in Figure 24.1, but if there is nothing to report, it won't appear on your computer. Here are some of the messages that might appear:

  • Network Discovery Is Turned Off—This means the service that locates other computers is disabled, or that all incoming connections have been disabled in Windows Firewall. Either way, icons for other computers won't be shown, and if you really did want network discovery turned off or the firewall completely blocked, their absence on this screen doesn't mean that there is a problem. If you are connected to a safe network (for instance, a network in your home or office but not a public Internet café) and you want to be able to share files, click the message bar and then click Turn On Network Discovery and File Sharing. This will turn on both functions and open Windows Firewall. If you only want to use others' shared files, click Open Network and Sharing Center and enable just network discovery.

    After you change the settings, view the Network window again and press the F5 key to refresh the display. Other computers should now appear.

  • File Sharing Is Turned Off—This means that Windows file sharing is disabled on your computer. You can still use files and printers shared by other computers, but others cannot use files or printers shared by your computer. This isn't necessarily a problem, unless you do want to enable sharing. To do so, click the message bar and select Turn On Network Discovery and File Sharing.
  • This Computer Is Not Connected to a Network—Your computer's network cable is disconnected, or your wireless connection isn't connected, or there may be a problem with your computer's network drivers. This is a fundamental problem: Your computer can't talk to any other computers.

Other messages could also appear. Click on the message to see what diagnostic and repair options Windows might offer.

If other computers still don't appear, and you know that network discovery is turned on and that Windows Firewall is open, it's possible that the network browser function, which is a behind-the-scenes service that Windows uses to locate other computers, is not working. This is a common problem. To investigate it, try these procedures:

  • Wait 20 minutes and press the F5 key. Other computers may appear this time.
  • Check each of the computers in your workgroup and make sure that each computer is set to use the same workgroup name and that each computer has the same set of network protocols installed. In particular, because Vista supports only TCP/IP, your other Windows computers should be reconfigured to use only TCP/IP and not IPX/SPX or NetBEUI.

For more information about networking with older versions of Windows, see "Networking with Other Operating Systems," p. 666.

The next step is to check the Network and Sharing Center to be sure that the network is enabled.

Network and Sharing Center

If other users can't use resources shared by your computer, the problem may be that the sharing services aren't enabled. You can get an overview of the networking services that Windows is providing from the Network and Sharing Center. To view it, click Start, Network. At the top of the Network window, click Network and Sharing Center. Figure 24.2 shows this window.

Figure 24.2

Figure 24.2 The Network and Sharing Center shows which networking services have been enabled.

Check the list features at the bottom of the window to be sure that the features turned on are what you expect and want. The features are as follows:


If Set to On

Network Discovery

Your computer will appear in other computers' Network folders, and other computers will appear in yours.

File Sharing

You can share files from your computer with other computers.

Public Folder Sharing

Your computer's Public profile folder will be shared on the network.

Printer Sharing

You can share your computer's printers with other computers.

Password Protected Sharing

Users of other computers will have to provide the name of an account that's been set up on your computer, and the corresponding password, before they can use your shared files or printers. If set to Off, anyone on your network can see your shared files and use your shared printers.

Media Sharing

Your computer's shared media (music and video) can be played by other computers and by media player devices on the network.

These first two windows covered the basics. If there's still a problem, it's time to let Windows have a crack at solving it.

Network Diagnostics

Windows Vista features a new network repair tool called Network Diagnostics that is said (by Microsoft) to be capable of recognizing and diagnosing more than 100 network problems. I'm skeptical of claims like this, but, on the other hand, it takes only a few seconds to let Network Diagnostics examine your network and offer whatever advice it can make, so it's absolutely worth a crack.

To run the Network Diagnostics tool, click Start, Network. At the top of the Network window, click Network and Sharing Center to display the window shown in Figure 24.2. Then, in the task list at left, click Diagnose and Repair.

Windows will display a box that says "Identifying the problem..." and will then display a results window that explains what was found to be wrong, what Windows did about it (if anything), what the outcome was, and where to go for more assistance. Figure 24.3 shows a typical diagnosis result.

Figure 24.3

Figure 24.3 Network Diagnostics tries to present an explanation and a solution.

If the Network Diagnostics Wizard doesn't lead you to a solution, the next place to go is the Event Viewer, which might have recorded informative error messages from network components.

If the diagnostics tool doesn't solve your network problem, check Windows Firewall to be sure it isn't blocking a desired network service.

Windows Firewall

Another configuration setting that could prevent file and printer sharing from working correctly is the Windows Firewall. To ensure that file and printer sharing isn't blocked, open the Windows Firewall window by clicking Start, Control Panel, Security, Windows Firewall. Then, click Change Settings and confirm the User Account Control prompt.

On the General tab, be sure that Windows Firewall is enabled (On is checked), and that Block All Incoming Connections is not checked. (This is unlikely to be the problem, however, because the Network window would have caught this, as discussed earlier in the section "The Network Window.")

For more information about configuring the firewall, see "Configuring Windows Firewall," p. 1222.

If the firewall settings appear to be correct, the next step is to check the Windows Event Viewer, to see whether Windows has left a record of any network problems there.

Event Viewer

The Event Viewer is another important diagnostic tool and one of the first to check because Windows often silently records useful information about problems with hardware and software in its Event Log. To display the Event Log, click Start, right-click Computer, select Manage, confirm the User Account Control Prompt, and then select the Event Viewer system tool. Select Windows Logs, and examine the System, Application, and Security logs in turn. You might also check for events under Applications Services Logs, Microsoft, Windows.

The Event Viewer displays Event Log entries, most recent first, on the right (see Figure 24.4).

Figure 24.4

Figure 24.4 The Event Viewer might display important diagnostic information when you have network problems. View the System, Application, and Security logs in turn.

Log entries for serious errors are displayed with a red X in a circle; warnings appear with a yellow ! in a triangle. Informational entries (marked with a blue i) usually don't relate to problems. Double-click any error or warning entries in the log to view the detailed description and any associated data recorded with the entry. The Error entry in Figure 24.4 indicates that my computer couldn't acquire a network address in a reasonable amount of time. It turns out that my router had come unplugged.

These messages are usually significant and informative to help diagnose network problems; they may indicate that a network card is malfunctioning, that a domain controller for authentication or a DHCP server for configuration can't be found, and so on. The Source column in the error log indicates which Windows component or service recorded the event.

These names are usually fairly cryptic. Table 24.1 lists a few of the more common nonobvious ones.

Table 24.1. Network Sources of Event Log Entries




Client for Microsoft Networks


Client for Microsoft Networks


Name resolution system for Client for Microsoft Networks

Application Popup

(Can come from any system utility; these warning messages are usually significant.)


Dial-up networking


Computer clock synchronization service


DNS client component


DNS client component


IDE hard disk/CD-ROM controller

If you're at a loss to solve the problem even with the information given, check the configuration of the indicated component, or remove and reinstall it to see whether you can clear up the problem.

To learn more details about the Event Log, see "Event Viewer," p. 878.

Device Manager

Hardware problems with your network card will most likely be recorded in the Event Log. If you suspect that your network card is the culprit, and nothing is recorded in the Event Log, check the Device Manager.

To use it, click Start, right-click Computer, select Manage, confirm the User Account Control prompt, and choose the Device Manager system tool. Any devices with detectable hardware problems or configuration conflicts appear with a yellow ! icon when you display the Device Manager. If no yellow icons appear, you don't have a detected hardware problem. This doesn't mean that you don't have a problem, but the odds are slim that your network card is the problem.

If devices are shown with ! icons, double-click the device name to see the Windows explanation of the device status and any problems. A device that you've told Windows not to use (disabled) will have a red X on it; this is generally not a problem.

For more detailed instructions and tips on device troubleshooting, see Chapter 28, "Troubleshooting and Repairing Problems," p. 965.

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