The hard drive, CD or DVD drive, speakers, monitor, mouse and keyboard all connect to the motherboard. The Dell GX280 motherboard provides pathways for the connected devices to communicate with the central processing unit (CPU), which executes software instructions. If the hardware devices aren't wired to the motherboard, the PC won't detect these components on boot up, and the computer won't run.
If the computer fails to boot on start-up, if you've disassembled the motherboard, or if you've removed or replaced a particular hardware, confirm all of the components are correctly wired to the Dell OptiPlex GX280 motherboard.
Turn off the computer, remove the power cable and disconnect all devices from the rear of the PC. Press down on the release buttons located on either side of the desktop, then lift the cover panel.
Shine a flashlight onto the motherboard to better identify the ports. Insert the floppy drive cable into the port labelled "DSKT." Connect the CD/DVD drive cable to the port labelled "IDE."
Insert the 7-pin SATA hard drive cable into the "SATA0" slot, found to the right of the "IDE" and "DSKT" ports.
Insert the front-panel connector into the port labelled "FRONTPANEL." The port is located to the right of the built-in speaker and coin-cell battery.
Locate a 20-pin power connector coming from the power supply. Plug the power connector into the "POWER" slot on the Dell GX280 motherboard.
Plug the 4-pin fan cable into the "FAN" port, found just to the left of the memory slots.
Insert the cables coming from the front panel of the computer into the front panel audio connector, labelled "FRONTAUDIO." The connector is located near the rear of the motherboard.
Insert the audio cable coming from the CD or DVD drive into the "CD_IN" port, found just above the "FRONTAUDIO" port.
Locate a square, 4-pin power connector coming from the power supply. Plug the connector into the "CPU" port next to the processor.
Reassemble the case cover. Plug the monitor cable into the blue 15-pin VGA connector. Connect the mouse and keyboard to the USB ports on the back of the computer.
Insert the speakers into the lime green line-out connector and insert the microphone into the light blue line-in connector.
Connect the power cable to the computer and turn on the Dell GX280 to test the PC.
These steps refer to the small form-factor and small desktop computer Dell OptiPlex GX280 models. The desktop, small mini-tower and mini-tower computer models use the same port labels on the motherboard, but may have a slightly different set-up. Unlike the small form-factor and small desktop computer, the mini-tower and desktop computer have a release latch on the case cover, rather than two buttons on either side of the case. When opening the small mini-tower case, push one button at a time while lifting the lid with the other hand.