Connecting a Pc to Internet using my own PC

Hi
I`ve been connecting my 2nd PC to the internet using my first connection to the isp using a network
On win xp it worked using the Network setup wizard
I`m using an Nvidia nForce Network controller (in which my ISP connection is) and have a second Network card 3Com etherlink 10/100 ( which is connected to the other pc sharing the internet conection) and it dosen`t work.
what can i do?

Try this:

Click Start and then type connections. Select View network connections. Right click on the network card that that has the Internet connection and select Properties. Click the Sharing tab, and then select the Allow other network users to connect through this computer’s Internet connection check box.

already tried that.
when i activate the option it busts the internet on my PC also.

start>run>cmd and type

NETSH winsock reset all