Can I make my PC redirect S/PDIF audio to my analogue speakers?

Basically what I done was connect my PS3 to my PC moniter as it's the only way I'll get HD, my parents have yet to make the jump. The thing is though, my moniter doesn't have speakers, so I thought I'd connect it to my PC using the S/PDIF input connection and hopfully my PC can redirect (or decode first if it needs to) the audio to my speakers, which are analogue. Is it possible?

Would I need to download any additional software?

Which cables are you using? You might be able to get a HDMI to a HDMI with sound port and then just put that into your speakers?

I'm using a S/PDIF from my PS3 to my PC and the green, orange and black (pic below) connection from my PC to my speakers.