|You need to review your motherboard manual. |
First of all look a 3-22 in your manual concerning sound settings in the BIOS. Also 4-4.
Do you have 2.1 speakers? That would be a sub with left and right satellite speakers.
If the satellites connect to the sub then plug the sub cable into the Green port and set for line out.
I know you said you can't select any ports. Go into the BIOS screens by tapping Del at start up. Set like it shows on 3-22 of your manual. 4-4 shows the sound manager for Vista. I don't know if it is the same for Windows 7 64 bit.