I started a new topic for you. It’s better to start a new topic even if the symptoms look similar.
Do you mean that in other programs you can hear sound in both headphones or speakers, but not in Audacity?
Are you choosing either the headphones or speakers as playback device in Device Toolbar ?
Is this Windows Vista, 7 or 8 or what version of Windows is it? If it’s Vista, 7 or 8, right-click the speaker icon by the system clock > Open Volume Mixer. Make sure the Audacity volume slider in Volume Mixer is turned up. Make sure the output volume slider is turned up in Audacity too:
Gale