I purchased an hp slimline s5-1400t to run my antenna through it. I have the computer hooked up to my sharp aquos via hdmi. Then an optical audio canle out to my receiver. Works fine except I realized now is that the computer won't detect the 5.1 speaker set up only stereo. I have tried hooking a 3.5 mm jack to my tv in then out via optical but it still doesn't detect it. Any ideas?
The optical out port on your tv only outputs 5.1 from the tv's internal tuner. Anything connected to it, the tv will only passthrough 2 channel stereo. You will have to connect the laptop directly to the receiver via hdmi or optical.
Why not run the HDMI to the AVR then from AVR to Display? That's the preferred method. Usinf SPDIF to the AVR is also acceptable assuming you have one... I looked online and finding the specs for your s5-1400t ain't easy... maybe you can post a pic of the rear looking for an optical out or an RCA coaxial (Digital) out.
BTW, you can usually find a $20 USB to SPDIF out dongle is you find you don't have one on the system and can't run to the AVR directly w/HDMI