Double-Check Your Network Settings | Networking For Dummies

I swear that little green men sneak into offices at night, turn on computers, and mess up TCP/IP configuration settings just for kicks. These little green men are affectionately known as networchons.

Remarkably, network configuration settings sometimes get inadvertently changed so that a computer, which enjoyed the network for months or even years, one day can't access the network. One of the first things you do, after making sure that the computers are turned on and that the cables aren't broken, is a basic review of the computer's network settings. Check these items:

TCP/IP settings: At a command prompt, run ipconfig to make sure that TCP/IP is up and running on the computer and that the IP addresses, subnet masks, and default gateway settings look right.
Protocols: Call up the network connection's Properties dialog box and make sure that the necessary protocols are installed correctly.
Computer name: Open the System Properties dialog box (double-click the System icon in the Control Panel), and check the Computer Name tab. Make sure that the computer name is unique and that the domain or workgroup name is spelled properly.
Permissions: Double-check the user account to make sure that the user has permission to access the resources she needs.