I have two computers (a laptop and a desktop) connected to a network using an Ethernet 10/100 Mbits switch. An ADSL router is also connected to the switch, providing an internet connection for the networked computers. Both computers can successfully connect to the internet, but neither computer is able to see the other computer. Therefore, I am unable to share files or printers between the computers. Running the Windows Network Connection Wizard does not help fix the problem, and if I attempt to access the workgroup the following message appears: ‘Mshome is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. A list of servers for this workgroup is not currently available’. The laptop is running Windows XP Professional and the desktop is running Windows XP Home Edition. Both computers are running Norton Internet Security 2006. How can I get the computers to talk to each other?

Diagnosing network problems without being in front of the hardware is a very difficult task. However, there are some common tests we can run to narrow-down the problem. First, it is known some security software can interfere with communications over local area networks. This is not just limited to Norton Internet Security, but many other packages can also cause network problems, especially when not configured correctly to work with the network setup. Therefore, your first test should be to disable Norton Internet Security on both computers. I would strongly recommend you only do this for a short period of time (as any time this software is not running you are potentially vulnerable to attack). I also recommend you disconnect the internet/phone line from your ADSL router to terminate the internet connection during this time, so that you minimise the chances of any attacks on your computer. However, do not disconnect the router itself from your switch, as it is likely the router is providing essential services for the network, such as DHCP (dynamic host configuration protocol - which assigns IP addresses to computers on the network). So, disconnect the internet line from your router, but don’t disconnect the router from the network.

If the computers can connect to each other with the security software disabled, it seems there is a misconfiguration in Norton Internet Security preventing communication of the two computers. In this case, you will need to go through the NIS software and correct this configuration issue. I cannot provide further advice on this aspect, since I do not run this software. However, at least you now know where to look. In the event the problem still continues, we should first check whether the computers can see each other’s IP address. You will first need to determine the IP address of the two computers. On each computer, go to the ‘Start’ menu > ‘Run’ and type ‘cmd’ (without the quotes) and click OK. In the DOS command prompt window that appears, type the following command:
ipconfig
You should see some information appear about your Local Area Connection. Note the IP Address of the computer. Once you have done this on both computers, you will now have the IP address of each computer. This is the network address of the computer, allowing each computer to be identified on your network. We will now check whether each computer can see the other. On one computer, open a DOS command prompt window (like we did above) and type the following command:
ping IP address of other computer
For example: ‘ping 192.168.1.2′. This will ping the other computer’s IP address, to check whether it can be seen. You should receive four replies to the ping. In this case, the computers can see each other, but you are unable to share resources through Windows for some reason. On the other hand, if you instead receive ‘Request timed out’ this indicates there is an underlying problem with the network configuration and the computers cannot see each other. In either case, there is a vast range of possible causes of this issue and most of these can only be properly explained and implemented if actually physically using the network. Your best chance of having this problem fixed is consulting someone to fix the problem on-site for you.