Probably simple - is the cable for the speakers plugged in
to the correct receptacle on the back of the computer ?
There can be 3 or 4 plugs that are the same size (mini-
phono) where the speakers plug in on the back of the
computer. Maybe someone accidentally unplugged the
speakers and then re-connected them to the wrong
receptacle.
Have you checked the volume - both in Windows and on the
speakers themselves - to be sure the volume isn't turned
down to the minimal level ? Or double-click on the
speaker icon next to the clock (lower-right) and be sure
the sound hasn't been muted for the device that's not
functioning.
Does ANY sound work ? Do the WAV files work (when
starting and closing Windows) ? If they do and the CD-ROM
sounds do NOT work, it's a cable inside the computer
between the CD-ROM and the sound card that's causing the
problem.
Are the speakers plugged in to a working power plug ? On
some speakers, if they're not getting power, they won't
work. Be sure there's an LED lit on the speakers.
Good Luck, let us know !