Weird Networking/Router Problem [SOLVED]

This problem is so weird that... I feel no one will believe until someone sees it for real ...I feel like a episode of Networking HOUSE MD.... so here goes

I have LAN using Netgear Router for my Small Office.

I have 2 New Computer with WinXP SP3 [Connected Via Ethernet Cable] and a Laptop with WinXP [No Service Pack] [Connected Via Ethernet Cable].

Now LAN works beautifully. No problem with that.

SYMPTOMS

The Problem starts ONLY when I connect the LAPTOP to the Router the internet stops working. Without THIS laptop connected, The internet works fine, between all the computers.....[added 2 more comp just to test and it works fine].

Once the Internet stops working I reset the router, the internet starts working for 5 mins and stops. BUT THE LAN CONTINUES TO WORK THROUGHOUT !

The is what I have tried so far.

1) Re-installed The OS of the LAPTOP
2) Removed the 2 Computers and connect only the Laptop to the router. And Internet works flawlessly. So problem can't be with the Laptop Network card.
3) Got my friends Router [same model Version 6] still the same problem.


I used to use this LAPTOP with the same router and a old comp without any problem. The problem started when I got the 2 new systems.

The problem occurs even when I connect the laptop with a wireless Network card.

This has got to point that I am obsessed as to why it isn't working !!!!

All symptoms looks like a conflict but what that conflict could be ?

ANY HELP appreciated... so that I can sleep again !

Thanks for the reply but MAC address was not the problem....

Turns out the problem was a maleware called unwise_.exe

I deleted it using MBAM !