If you looked too quickly and guessed ATX, take another gander. At a glance, it might look like a standard ATX motherboard, but it's actually an Intel D955XCSLKR motherboard in the failed BTX form factor.
Intel proposed replacing the circa-1996 Advanced Technology eXtended form factor in 2004 with the Balanced Technology eXtended form factor. Among BTX's big changes were relocating the CPU to the very front of the motherboard, so it could receive cool air that was sucked in from the front of the case.
BTX also relocated the south bridge controller chip for such things as USB, closer to the rear of the computer where most of the ports come out. It ultimately failed, because most vendors didn't want to retool. Also, CPUs were evolving from nuclear furnaces (looking at you, Pentium 4 Prescott) to super-efficient, cool-running components.
BTX didn't achieve popularity with builders, but big PC vendors adopted it for a few years, and many systems are still out there with BTX boards today.