Here's a basic layout for you...
On the 2Wire Router, there are likely 4 ports that are numbered. Connect port 1 to your MCE PC. Connect Port 2 to the ethernet jack in your home's wiring. If the jack in the wall is connected to the switch, a light should come on at both the 2Wire router and the Trendnet switch.
Connect the Xbox 360 to the port in the wall. You should see a light turn on at the back of the Xbox 360 to show connectivity to the Trendnet switch as well. If you view the Trendnet switch there should be 2 ports showing connections (assuming there are no other active computers connected in the house).
The only thing that I am confused about is what type of cable is feeding the 2Wire router. There must be some form of input. Is it a coax input?
Hope that helps!
1: Dimension 9200 - Vista Ult, 2.4GHz Q6600 Core2Quad, 4GB RAM, 160GB, 750GB, 500GB USB, Nvidia 8300GS, PVR-150, HDTV Wonder, Vbox 3560, X360, DMA2100
2: HP m376n - MCE 2005, 2.6 P4 w/HT, 1GB RAM, 250GB, 400GB USB HD, Nvidia 6200, Emuzed MAUI, X360