Two places where the fault may be:
The phone "socket" at the speakers and the "plug" of the earphone. They may not fit properly. Try pulling out the plug slightly or not pushing it in all the way, or giggle it a bit, etc. and see if it works. Try another pair of earphones. Else the "socket" may be broken (contacts rusted, worn, or electric contact cannot be made).
This isnt a question relatd 2 operatin system but il b glad if sumone helps me.im using vista ultimate.when i connect my earphones or headphones to the speakers nothing comes of it.absolutely mute.this is not related 2 vista as i had same problem in xp.the speakers are absolutely workin and d headphones and earphones work welll when connected to any other device except computer speakers.no problem wid any of the hardware.can play sound when headphones not connected to speakers.