A computer system includes a chassis and a frame. The chassis includes a chassis bottom wall, a first chassis sidewall connected to the chassis bottom wall, and a second chassis sidewall connected to the chassis bottom wall. The frame includes a mounting bracket and a retaining bracket. The mounting bracket is secured to at least one of the chassis bottom wall and the first and second chassis sidewalls. The mounting bracket defines a through opening configured for to have a disk drive inserted through the opening. The retaining bracket defines a holding space configured for receiving the disk drive. The through opening is in communication with the holding space. The mounting bracket includes a mounting bracket top wall. The retaining bracket includes a retaining bracket top wall. The retaining bracket top wall extends from the mounting bracket top wall.