The adapter that Chris L listed only works if your HDTV will output STEREO via the optical output. Your HDTV is a 5.1 device so unless the TV Audio setup menu lets you output PCM/LPCM which is code for 'stereo', that converter will not work. (read the customer comments below the listing on the Amazon page).
Computer speakers are designed to work with computer sound cards, not home theater gear.
