Things You'll Need
Instructions
Plug the USB modem into your computer and turn on the PC.
Connect to the Internet via the USB modem. If the modem is a wireless modem, you will need an accessible wi-fi connection to do this.
Plug the ethernet cable into the ethernet port of the computer, and the other end into the ethernet port on the Xbox 360.
Access the control panel on your computer and go into the "Network Connections" window.
Right-click the connection that represents your USB Modem and select "Properties" from the dropdown menu.
Click the "Advanced" tab, then ensure that the "Allow other network users to connect through this computer's Internet connection" option is selected. Click "OK" to exit.
Turn on your Xbox 360 and sign in with your profile. The Xbox will automatically detect and connect to the Internet connection provided by the USB Modem through the PC's Internet connection sharing.