According to Microsoft, users experiencing speaker problems should first check to ensure that speaker cables are connected. Speakers sometimes have volume control knobs and power buttons as well, so an obvious step is to ensure that the speakers are powered on and have their volume turned up.
If the problem persists, check the "volume" icon on the computer's task bar and make sure it is not set to "mute." Problems with a sound card can mimic speaker problems, so sound card drivers must be checked to ensure that they are running the most up-to-date version. Using a pair of speakers that are proven to be functional can help uncover the source of speaker issues.