I have a feeling that I have no idea what I am doing. I purchased a new PC from one of those custom, build-your-own PC websites. I just installed Windows XP (It came with no OS installed). The computer is connected to a Linksys 10/100 switch (other computers are connected to the switch and can reach the internet fine). I set up a new network connection on the new computer (1394 Net Adapter). The connection status reads "connected" even when unplugged from the network. The switch does not recognize that the new PC is connected to it (the lamp doesn't go on). Typing ipconfig does nothing (it prints out "Windows IP Configuration" followed by nothing). What is going on...? Am I an idiot?

No, you just tried to configure the wrong network connection. Undo what you did to the 1394 Net Adapter and ensure your Local Area Connetion (NIC, not 1394) is enabled and from the sounds of it, set to DHCP.

Check your device manager (my computer > properties > hardware) and make sure there arent any yellow ? next to your network adapters. Recently had about the same problem you had after I reformatted my old comp. What your talking about sounds like its the issue. Hope it helped, Garrett

There seems to be one network adapter (the 1394 net Adapter). I didn't order an NIC because I thought that there was one built onto the motherboard (where did I get this idea? Is that even possible?) Is the problem that I do not have an NIC?

It might be. First, check the back of your PC for an RJ-45 (network) plug. If the motherboard has a built in NIC, there will be a port on the back. If you don't have one, then you'll have to purchase a NIC and install it...then configure it. If you do have a built in NIC, the drivers may need to be loaded. Do like Garret said, check in Device Manager for a NIC (Network Adapter). If you have one listed there, you may need to update the drivers. If it's not listed in DM, then you have to install the drivers which are likely on the motherboard CD-ROM that came with the mobo.

Thanks a lot guys. The problem was that I hadn't installed LAN driver from the mobo CD. I am now connected to the internet and very happy :)

Always a pleasure to help!