surround sound setup for pc, help needed! :)

I am trying to setup up an old-ish (i think) surround sound system on my pc, the system is the TA-VE215 along side the SA-WMS215 (both sony i believe). I basically have no clue how to set this up, i have got the front right and left working, as well as the center working, but the rear left and right do not appear to work, any suggestions??