A Dell computer's sound might not work various reasons, including incorrectly connected power cables from the speakers to a wall outlet, or audio cables not being plugged into the audio port on the computer. Sound problems can also stem from incorrect settings in the operating system.
Sound issues can also arise from corrupted driver software for the computer's sound card. Check the Device Manager portion of the operating system for the sound card manufacturer and then, according to Microsoft as of 2015, check the manufacturer's website for an updated driver. Alternatively, updated sound drivers may be available through Microsoft's Windows Update feature.