The LAN (local area network) connection for my computer has disappeared. I have tried to install new hardware several times on the control panel, and to try and set up the connection from control panel, but to no avail. I am running a Dell Inspiron 600m.

Can someone please help?

I'll assume you are using a wired connection and XP here. Instead of just trying to install new hardware, you might want to try to uninstall the network interface card (NIC) from device manager first, then restart and then try to reinstall it if it doesn't get picked automatically by windows.

You can get to device manager easily by right clicking on My Computer then choosing Properties. When the System Properties window opens go to the Hardware Tab and device manager is right at the top. If your NIC isn't highlighted as having a problem look under Network Adapters and see if a device is listed that mentions Ethernet. If its listed, right click and choose uninstall then restart. You may need to download the latest drivers for the card but without another PC connected to the internet that may prove troublesome.

Have you also tried the Create New Connection wizard under Network Connections in Control Panel? You may be able to choose "Set up a Home or Small Office Network" in there. It might give you more of a clue where the problem lies.

Is the Network Connections Service started? If this service is disable or stopped, your Network Connections Folder will end up empty.