sound problems... :(?

I checked everything possible, the plugins are in the right spots, the computer says the speakers are working just fine,the volume turner on the speakers is on,the speakers are brand new, so is the computer. Dell inspiron 546. Also, When i plug in a new head-set into the headset plugin, no sound still. And just yesterday before shutting down and unplugging the computer, the sound worked just fine.... I'm puzzled at what is wrong and hope someone on here could help me with this *issue*. :(

Thanks to those that can. :)