If there is more than one speaker output connector on your PC then you can be sure the sound device fitted inside it can output more than 2 channels. A 2-channel device only has one speaker output connector. There should be a control panel for your sound output (either in Windows Control Panel or listed in Start->All Programs, where you should be able to set it to 4-speaker output.
Go into Control Panel->Sounds and Audio Devices. Click on the bottom 'Advanced' tab in the 'Speaker Settings" section, there you will see a drop-down list under "Speaker setup".
Select the speaker configuration which applies to your speaker setup. I imagine you need to select either "Quadrophonic speakers" or "Surround Sound Speakers".
Edited by pip22, 29 October 2007 - 07:51 AM.