To Genesis 15,
I see you followed the concensus advice and bought a router. Rather than be a total jerk and say ha ha I told you so, I must instead honestly tell you that there is almost certainly something wrong with your living room computer and if you went crossover cable and ICS, you probably would be in the exactly the same boat.
But you are in troubleshooting mode now, I looked at the links, and you are getting some great advice. A large number of things could cause this limited connectivity, and you should follow each step, step by agonising slow step, until you find the cause or causes.
Its even possible that some of your new hardware is defective----if you have a friend with a laptop computer, it might be good to see if you can add it to your network---which could do alot to show certain pieces of hardware are known good if the lap top connects. On the bright side, you will get a good education in the process.
And if, at the end of the rainbow, it turns out to be a corrupt winsock, I will point out that is often due to malware getting onto the computer.---still not worried about computer security?