Check whether you plugged in the speaker wire into the correct jack at the
back of the computer (it should go into the green colored jack on the sound
Did you try playing a sound file? Does media player show the file as playing,
but you can't hear anything? Or do you get any error? if there's any error,
please mention the error.
If the sound plays but you can't hear anything, again, check the speakers are
connected to the correct sound jack. Next, try connecting a pair of headphones
or earphones (lower the volume before playing any sound or music file).
If you still can't hear anything, click Start and type the command "dxdiag"
in the Run box and then press the Enter key. In the dxdiag window, click the
Sound tab. Check the Notes box, if it gives any error info. If your card is
working, it should say 'No problems found." You can also test the sound using
the "Test Directsound" button.
If you still can't hear any sound, you should check and reinstall your sound
card driver manually after removing it first.
There may be other problems. For more information, check
this nice blog post about sound problems
Hope that helps.