Before you begin: Remove the side panel, the optical drive, if installed, the front bezel, the wireless LAN module, the expansion cards, if installed, the hard disk drive. Note: You don’t need to remove the hard disk drive from the drive cage, the fan duct, the fan and heat sink assembly, and the CPU. Removal Disconnect the following from the motherboard: CPU power cable, Main power cable, Power supply command cable, SATA power cable, SATA data cable Remove the nine T15 Torx-head screws that secure the motherboard to the chassis. Partially lift the front of the motherboard upwards. Carefully slide the motherboard to the front of the chassis to release the connectors from the rear I/O panel. Lift the rear edge of the motherboard and carefully pull it out of the chassis. Replacement Before replacing the motherboard, you must first restore the CMOS factory settings. Remove the RTC battery from its socket on the motherboard. Wait thirty seconds. Replace the RTC battery to its socket on the motherboard. CMOS factory settings are now reset. Grasp the motherboard by the edges and carefully insert the front edge of the motherboard at an angle into the chassis. Lower the motherboard onto the chassis and align it with the metal tabs on the chassis. Toe the rear I/O connectors into the rear I/O panel until the motherboard sits snugly in place Replace the nine T15 Torx-head screws to secure the motherboard to the chassis. Reconnect all of the connectors to the motherboard. NOTE: After reassembling the desktop, you need to enter system BIOS, and reset the time and date settings in BIOS.