install/reinstall your NIC driver. your motherboard/computers manufacturer will have the driver available on their website. download it on another computer then transfer it how ever you can. thumb drive works well.
i have windows 7 ultimate and in the system tray there is a red cross on internet, it was working fine before i just rebooted my windows . no cd was provided by the isp when i connect the ethernet cable to another computer the light on the router start and i m able to use . plzz help me some