I mounted a full size ATX motherboard and power supply without problems. The Centurion 531 does not have a removable motherboard tray, but that is the norm for many lower cost enclosures. Cooler Master uses threaded brass standoffs to securely mount the motherboard to the chassis. The power supply, motherboard and AGP/PCI cards lined up perfectly in their respective openings.
The Centurion 531 uses tool-less PCI slot retention clips that were literally a snap to use. Push and rotate them one way to unlock; rotate and snap them into position to hold the card in place. While easy enough to use, they didn’t seem to lock all cards in position as securely as I would like.
Luckily, Cooler Master also provided tapped holes at the top of each expansion slot, so expansion cards can alternately be locked in position with standard machine screws.
The Centurion 531 incorporates a removable hard disc drive (HDD) cage, which can mount up to three drives using the provided plastic rails.
The five optical drive bays and upper two 3.5′ drive bays use sliding plastic latches to secure the drives in place. Each of the drives I installed mounted securely and lined up well with the front bezel. In addition to the plastic latches there are holes for use with conventional mounting screws if you prefer to go that route.