LAN port not working

[suniltr77]

I am facing this problem for last couple of months. I am unable to use the LAN for the Internet or networking.When the power is supplied to the CPU and modem, the LED for LAN in the modem glows, but as the computer boots after 2-3 sec the LED diminishes and there will be no network connection after the computer starts.I have tested the Mother Board as well as the Modem individually and found OK. I tested removing one by one the graphics card,audio and tuner but nothing gave me any result.
Can somebody suggest any solution?

[pimpom]

Which OS?
Could you use the LAN port earlier? (I'm assuming that you're talking about an onboard LAN port).
What do you mean when you say that your motherboard is OK when tested individually?

[suniltr77]

I was using the modem with on board LAN port. Suddenly it didn't recognise and showed me no network connectivity. I thought cable might be damaged, changed but still no solution. I checked with another computer with that modem, it worked. So I thought my LAN port has a problem. I checked the MB with other desktop, it worked fine. I can't figured out what can be a problem.
I am using the same modem with UBUNTU in USB mode. I am unable to use the modem with WIN 7 as I don't have the driver. I have got 2 modems 1-MT882 and 2-C2110 Nokia siemens. Both are not working with WIN 7 in USB mode

---------- Post added at 08:08 PM ---------- Previous post was at 07:49 PM ----------

I think I must step back to XP to use something I missed in UBUNTU i.e. VOIP facility in Gtalk