You will either need
to adapt the mini-phono analog stereo output of the pc to traditional RCA
connections and attach them to the (likely) mated audio input associated
with the HDMI input of the TV. Or, you can run the digital audio output of
the laptop into a similarly mated digital audio input of the TV. Both of
these would be parallel connections. If running another cable isn't viable,
then there are modular technologies you can buy that will integrate the
audio into the HDMI at the PC side. The composting would still occur
outside the PC, but if your HDMI is in the wall or something, then this
approach is likely more feasible. Check gefen dot com - no, I don't work
there. (Gefen's would require you spot adapt the HDMI to DVI - it has a DVI
input and a digital audio input - and voila, one HDMI output w/ audio. Good
luck (also applies to many other video cards, by the way.)

thanks