This switch-box switches the analog multichannel inputs of the receiver between the DVD (Audio) player and the HTPC (leftmost switch). The next switch switches between 5.1- and 7.1 mode on the receiver. (In 7.1-mode, the receiver expects Left and Right front channels not on the Multichannel inputs, but on ordinary analog inputs. Instead, "Front" and "Right" on the multichannel inputs are routed to the back surround speakers.) Finally, with the third switch, it can be selected whether the Windows "side speakers" or "surround speakers" will be routed to the left and right surround speakers.
Remaining switches have no function.