Things You'll Need
Instructions
Turn on your computer and plug the USB modem into a free USB port on said computer.
Open the Control Panel once the operating system has finished loading and click the following icons: "Network and Internet" -> "Network and Sharing Center" -> "Manage Network Connections."
Right-click the connection that pertains to the USB modem and select "Properties."
Select the "Sharing" tab and ensure that the checkbox labeled "Allow other network users to connect through this computer's Internet connection" is selected. This will allow other devices---in this case, the Playstation 2---to connect to the Internet using the USB modem's connection, provided they are connected to the computer via an Ethernet cable.
Plug the Crossover Ethernet cable into the Ethernet port on your computer, then plug the other end into the Ethernet port on the back of the PS2.
Connect to the Internet via your USB modem if you have not already done so.
Insert the game disk you wish to play online with your PS2 and connect to the Internet as usual. The PS2 will detect the USB modem's connection, thanks to the ICS you set up in the previous steps and will be able to utilize the connection for itself.