How to connect Laptop to Sony HT-DDW750

[itsperams]

I recently got a Sony HT-DDWt50 home theater system from one of my fiends. I got a HP pavilion laptop. I tried connecting the laptop and HTS with 3.5mm stereo to RCA Red/White audio cable to connect the two, but the audio output is not coming in the HTS.

 

[americanaudiophile]

Make sure that the laptop is putting out audio by connecting headphones to it.
If it doesn't work then check the laptop audio or video control panel. You may be sending audio through the HDMI output.
If it works then make sure that you have selected the correct input on the HTS. Try a different cable.

 

[itsperams]

Make sure that the laptop is putting out audio by connecting headphones to it.
If it doesn't work then check the laptop audio or video control panel. You may be sending audio through the HDMI output.
If it works then make sure that you have selected the correct input on the HTS. Try a different cable.

Thanks @americanaudiophile for your reply. I did check the audio output from Laptop to headphones. They are working, even I connected simple speakers to Laptop they are giving the audio output too.
As I mentioned I connected Home theater and Laptop with a 3.5mm stereo to RCA audio cable. It's not through HDMI output. I've tried all the inputs on the HTS but no luck. I bought a new 3.55mm/RCA cable and tried too but still no output from the HTS. Unfortunately there is no HDMI input connection on HTS, should have tried with the HDMI cable if that exists.

Any other suggestions...