Abstract: A low profile personal computer includes an enclosure having a bottom wall. A riser card including functional circuitry extends vertically from the bottom wall and partitions the enclosure into first and second regions. A motherboard is positioned within the first region of the enclosure along the bottom wall and adjacent to the riser card for interfacing with the riser card. A series of horizontal option card interfaces are located above each other on the riser card within the first region of the enclosure each for interfacing with a corresponding option card and to position the option cards horizontally over the motherboard. The horizontal option card interfaces are capable of interfacing with a maximum of three option cards at the same time. The functional circuitry on the riser card minimizes the number of option cards which enables the overall height of the enclosure to be minimized.