First, sorry for the topic, but I didn't find any solution for my problem.
 
I have an Abit A8N motherboard with nForce4 chipset, and my lan port doesn't work. I don't know, what can be the reason of this problem, but it's annoying enough.
I set the value in the BIOS 'Enabled' and installed the driver of my motherboard.
Rarely the LEDs of the lan port are blinking, but when I sign up Windows, the system says: "Network cable is unplugged" .
I read many forums, and - I think - I'm not the only one with my problem, but I didn't find any good solution.
 
My short story: 2 days before I tried to plug a lan cable into my lan port (beetween a ruter and my PC), and i wondered that the led's are blinking. After that I installed the Windows, and during the installation the led-s shows that the lan is operating. Well, XP is done, I must install motherboard drivers...but when the setup utility makes the lan driver, it shows "Network cable is unplugged" again.
 
Is this a configuration problem, or a hardware failure?
 
I haven't got any idea to solve my problem, please help me!!! Thanks...

In BIOS  'enable' all options associated with LAN, like I have an NF4 board I have to enable Nvidia LAN and the ethernet adapter shows up in Device manager.  Should be under 'onboard devices' or something similiar.

It's okay, but there is just one option in connection with LAN, I think (or not?). This is "LAN Controller" in BIOS. It's 'Enabled' and I see the "Nvidia Nforce Networking Adapter" in the Device manager. The windows says: "This device is working properly.", but it doesn't work.
This is the reason, why I don't understand my problem.

Yeah, I have just gone through this with an old NF4 board, the Nvidia Nforce Networking Adapter showing in Device amnager, configured correctky, but not being able to establish a connection (Right?).  I concluded I ran a Registry cleaner and corrupted the registry.  That's what I came up with, the registry was corrupted.  I reloaded the OS and it fixed it!  I'm using the system now.

Registry? I think, it's not in connection with regisrty, because I tried it 4 different operating system, and the problem is the same. But the registry is clean...
(or we misunderstand each other?)

Yeah, not sure we had the same problem with the 'Nvidia Nforce Networking Controller'.  I had to enable this controller in BIOS to get it to show up in Device manager.  The Controller was configured correctly.  I could not establish a network connection.  Finally, I reinstalled WIN XP, enabled the Controller in BIOS and everything works perfect.  

Yes, unfortunately my problem is a bit different. But thanks for the help!

 
 
What kind of networking cable do you have plugged in between the router and LAN port on your computer?  If it's a crossover cable it might not work.  Otherwise you may have either a bad cable, or something messing up inside the port itself on the motherboard.

I use a normal Cat5 cable. It's not a crossover one. It works, because it was used before.
What do you mean by "something messing up inside the port itself on the motherboard"? Thanks...

 
Like a chunk of dust or dirt coving up one of the connector pins.  Or one of the pins on the cable or port being corroded/rusty things like that.  How long ago was it used, and try and test it on another computer.

Cable is good, because I have a router and a switch too. If I connect the cable beetween the router and the PC, it doesn't work, but it works beetween the switch and the router.
The lan port of my mobo is "physically" good, because randomly it indicates me about the traffic. But just randomly... :S