you need to setup a network bridge between the tower pc and the xbox 360
Select Control Panel/Network Connections and while hovering over Network Connections, right click and choose Open. This will open a panel that should list your network connections.
This image shows all my existing network connections. Yours may not have the same adapters. The two adapters that matter are your wireless adapter and your Ethernet adapter. They will have different names than mine because I have renamed them from their default values. I have highlighted the two adapters in the graphic below.
If you have both Ethernet and wireless adapters (and you must in order for this to work), then both of them will be listed in the Network Connections panel. Using the ctrl-click selection method or the drag-area method, select both adapters.
Right-click one of the adapters and select the Bridge Connections
You will see a notification that the bridge is being built. This may take a few moments.
Once the bridge is complete, you will see the bridge icon and the network adapters as shown below:
The bridge is only partially complete at this point. To complete the configuration, you need to relate the network adapters to the bridge. I’m not exactly sure why this is because you have to select the adapters to create the bridge in the first place. This is my first bridge, so it’s possible there is a better way of doing it. But this process has worked for me. If you know of a more concise way of configuring the bridge, let me know and I’ll update the process.
In any case, select the bridge, right-click and select Properties:
In the Properties dialog, put check marks in the network adapters that you want to bridge. Make sure you select the wireless and Ethernet adapters.
Now, the bridge is complete. It will take a few moments for your laptop to finish the configuration, get a new DHCP lease and complete the connections.
To verify if your bridge works, connect the XBox 360 to your laptop’s Ethernet port and connect with XBox Live.