1. Open My Network Places and click View Network Connections. Find the
connection that usually links you to the internet - normally in the 'LAN or high¬speed internet' section. If it's shown as Disconnected, check the cables, and make sure that other devices are powered-up correctly. Vista users should click the start menu, and choose Network, then Network and Sharing Center.

2. Double-click the connection and then click the 'Support' tab in XP to check that the computer has assigned an IP address, and that it looks like a valid one for your network - the first three numbers will almost always be the same. Click Details to see options such as DNS addresses. Vista users click 'View Details' and then 'Status' to see the same information.

3. Try using Windows' built-in Repair option. This will request a new IP address from your network, and will fix things if, for example, the PC was turned on before the broadband router. XP users just need to click the Repair button on this screen, while in Vista, click the Diagnose button and follow the on-screen instructions.

4. If you can access your router from another computer, check that its DHCP server is turned on, and that the settings are correct. If none of the computers can connect, try turning the router off for a short while and then back on again. With this done, attempt to repair the connection again in Windows.

5. Hopefully your computer has a valid IP address by now. If it still can't connect to some programs or sites, check the Windows firewall via the Control Panel on XP or the Network and Sharing Center on Vista. Make sure there isn't a tick in the 'Don't allow exceptions' box on Xp, or the 'Block all incoming connections' box on Vista. Check that the programs you want to use have a tick next to them on the Exceptions tab.

6. If you have difficulties with file sharing on the local network, open the System option in the control panel, and check the Computer Name. Make sure the workgroup is set to the same option on all the PCs. If you're trying to connect to a Vista computer you'll need to disable password protected sharing or use a valid user account and password.