I'm sure I'm not the first to be disappointed by the placement of the output ports on his Xbox360, specifically how the old trapezoidal A/V cable plug blocks the HDMI port on the Elite models. And Microsoft, being the conniving #$%^ers they are, have come up with a handy $49.99 solution
to the problem that just so happens to be entirely irrelevant.
My problem came about because I wanted to hook my 360 up to my 22" widescreen monitor which doesn't have audio. Obviously I didn't want to play without sound and my attempt to plug the HDMI cable and the A/V cable in simultaneously met with futility.
My solution involves modding the Microsoft Composite A/V cable, which should have come standard with the system. I realize now, after doing a quick Google search, that there are a few other tutorials online on how to do this so I don't claim any credit for originality.