A computer includes a casing; the computer further comprises a motherboard, a hard disk drive mounting structure and a hard disk drive accommodated in the casing. The motherboard is mounted on a fixing plate of the casing. The hard disk drive mounting structure is located above the motherboard, and includes a heat dissipation apparatus including a heat sink, a mounting frame, and a supporting bracket connected between the mounting frame and a base of the heat sink. A bottom end of the supporting bracket is fixed to the base of the heat sink. A top end of the supporting bracket is fixed to one end of the mounting frame to support the mounting frame, which has another end fixed to a side plate of the casing. The hard disk drive is mounted on the mounting frame.