Do you have things like Zonealarm running in the background?? Was the 2nd. PC already switched on when you installed networking?? Is the 2nd. PC's ISP address higher or lower than the main PC??
Are you using a Router??
Zonealarm - Go to Trusted & Internet & Allow/Trust BOTH pc1 & pc2.
Router - Has to be set up to allow both PC's. This usually involves typing in
click here - then you have to allocate a fixed isp address for each of the computers.