Make sure the speakers are plugged in and are powered on and the volume is turned up. Make sure the audio cable from the speakers is plugged into the Back Green Audio port of the desktop computer not the front.
Go to Control Panel/Sounds Playback tab. Make sure your Speakers are selected. Press the Configure button. Press the Test button. It should play a series of tones thru the speakers Make sure the Speakers are the Default Playback device.