subwoofer gateway 610xl machine won t work 5 1 surround

My Gateway 610XL's center/subwoofer won't work.
Gateway calls it a One 5.1 Line Out consisting of Front, Rear, Center/Sub. My computer bluescreens whenever I try to test the 5.1 speaker config in the volume control. My computer isn't picking up 2 driver
When I test the 7.1 the subwoofer makes a sound. (A crappy sound compared to Stereo test) But, when I go into media player the sub doesn't play.
My computer isn't installing 2 "Unknown device" drivers. I'm not sure if it's related. i tried installing the drivers for XP, but when I go into the Sigma speaker wizard I get a can't open sound mixer error message.
This is on a clean install of vista. When I upgraded from Media Center 2004 before the clean install the computer would bluescreen whenever I played sounds or tried to log in.
Computer specs: http://support.gateway.com/s/PC/TVMediaCenter/2900005/2800347sp11.shtml
Thanks in advance.