Subwoofer in Gateway 610XL machine won't work (5.1 surround sound?

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/TVMe...0347sp11.shtml

Thanks in advance.