Realteck 5.1 (6 channel) sound problem

Hi,
I have finally got round to connecting all my speakers up to my fairly new
PC. I have a Soundblaster desktop 5.1 speaker system and my new mobo, aa
ASrock N68PV-GS, has 3 rear connectors for the onboard Realtek ALC662
system. I connect up my 3 cables, Front Green to Green on the mobo, middle
black/blue and the centre/bass pink/orange to the mic in. The Realteck
control panel objects to this mic connection. No matter what I try I get
everything via the two front speakers. All is set up to 5.1 in the control
panel, I have checked all my cables are well seated and in good condition.
I have installed the latest drivers so what am I missing please.

Thanks in advance,
Dave.