have hp pavillion using spdif out to an audiovox dv1300c coaxial in. no sound. why?

Question

have conversion cable; spdif to RCA

Answer 1

s/pdif is DIGITAL
RCA is analog
So, in order to go from digital to analog you need some audio processor in between otherwise nothing will work. I am sure your HP Pavilion has analog out. So, why don't you connect analog out from the Pavilion to the Audiovox?
Is your Pavilion a TV or a PC?
s/spdif is used for multi-channel audio. If you have no multi-channel source and you just want stereo audio, use RCA stereo from the source to the receiver.