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Network Problems

When I upgraded my home network by adding a third PC, the new machine couldn't connect with the other PCs on the network, nor could it access the Internet. What do I do now?

Andy Ferguson, pastor, Cleveland, Tennessee

Installing or upgrading a Windows network at home or work isn't nearly as complicated as it used to be, as long as everything goes smoothly. Run into a glitch, and you can lose hours as you try new settings (some of which may add to your problems). But you don't need to.

Your first step should be to rule out physical connection or hardware problems. Check your network adapter to confirm that the lights indicating a good connection are lit. If they aren't and you're on a wired network, check your cabling. If you're on a wireless network, run the installation routine for your wireless adapter one more time and double-check your network ID and encryption settings.

If the PC's connection is good, but it won't connect to the Internet, it may have an incorrect IP address. To assign a correct one, you need to ensure that your network uses exactly one Dynamic Host Configuration Protocol server (which assigns a unique IP address to each computer on your local network), check that the DHCP server is on, and confirm that the new computer is connected to the network.

Here's how to check for DHCP: If your modem is connected directly to a computer that then shares that connection with other PCs on your network, you've set up Internet Connection Sharing (available in Windows 98 and later versions) or a similar program, and it is your DHCP server. If you're using a router, you'll find an "enable DHCP" option in the router configuration software that you can access via a Web browser on one of the working computers on the network. Double-check it, and while you're there, make sure that you have set the number of users high enough to accommodate all of your (and your guests') PCs and notebooks.

Now reboot the new PC, and see if you can browse the Internet. If not, the easiest way to get all the necessary default settings is to remove and reinstall your system's TCP/IP protocol. If your new PC uses Windows 98 or Me, open Control Panel, open Network, select TCP/IP * [ network card] (where [ network card] is the name of your network card), and click Remove*Add*Protocol*Add*Microsoft. In the right pane, choose TCP/IP, and click OK. Press <Enter> when asked if you want to reboot your PC.

For a Windows 2000 computer, select Start*Settings*Network and Dial-up Connections. Right-click the icon for your network, and open its Properties dialog box. Then select Internet Protocol (TCP/IP)*Uninstall*Yes*Yes*No. Once your computer has restarted, reopen the network Properties dialog box, and select Install*Protocol.Add*Internet Protocol (TCP/IP)*OK*Yes.

XP won't let you uninstall TCP/IP, so you must reset its default TCP/IP settings manually: Open Control Panel, open Network Connections, right-click your network icon, and select Properties*Internet Protocol (TCP/IP)*Properties*Obtain an IP address automatically*Obtain DNS server address automatically*OK.

While we're here, click the Advanced tab and make sure that the Protect my computer... box is unchecked. Click OK and Yes if asked whether you're sure you want to turn off Internet Connection Firewall. If your network is router-based, you have sufficient protection without a software firewall like XP's ICF. If one of your PCs shares its Internet connection, your firewall belongs on that system. If you don't already have one, we recommend Zone Labs' $50 ZoneAlarm Pro 3, which automatically senses when ICS is running and stops intruders without affecting local network access.

For a more comprehensive look at network setup and troubleshooting, check out May's " No-Hassle Networking Guide."