Lost connection after reformatting laptop

I am using a NETGEAR router at home with my desktop PC. My laptop can connect to it through an RJ45 cable wire. And I never had any problems with it for the whole time of using it. When my laptop had a virus, I re-installed my Windows XP but the problem is I cannot connect to the router again. The error is stating that the LAN has been unplugged. Am I missing any software or is there an issue with the router itself? Help please.
