A crazy subwoofer problem with my PC (Resolved, thanks to super-dude Malor)

I'm about 90% moved to a new house, free from noise-sensitive neighbors. This makes me ecstatic, as I can finally hook my subwoofer on my PC back up. (Or, well, hook it up for the first time;it's never had a sub attached.)

In a cruel twist of irony, I can't get the subwoofer to work properly. Here's the system setup:

Running a dual-boot OS; Windows 7 (64-bit) and Windows Home (32-bit), service pack 3.
Dual Core e8500
4 gig DDR2
Radeon 5850
Audigy X-Fi Gamer (it's a SB0770, sort of an unusual OEM Dell pull card with optical connections)

The system is connected through the audigy to a Yamaha receiver with 6-channel input. The six-channel input allows for the standard front left, front right, center, rear left, rear right, subwoofer.

The Yamaha is connected to the appropriate standalone speakers.The subwoofer pre-out is connected to a powered 10" Sony subwoofer.

In the Creative audio console, the subwoofer works fine. All channels respond properly, the subwoofer gives a nice beefy blat.
In the THX setup console the situation is the same; all channels respond properly, subwoofer definitely firing. System is set to 5.1.

This is where it starts to drive me nuts. NO OTHER APPLICATION will use the subwoofer! Games, iTunes, test tones playing through my browser, etc. Nothing! No other program will send so much as the tiniest signal to the subwoofer. Back in the test console/THX setup, everything is fine.

This situation happens identically on Windows 7 and XP.

I've tried switching the subwoofer connector at the yamaha with the center just to test; the center channel information then comes out of the sub, so I know it's receiving data. It's just not being sent a signal from any other application.

Any idea of other test programs that can help resolve this? I have an audigy 2 ZS that I can throw in for additional testing.

You have to turn on "bass management" in the Audigy control panel, and choose a crossover point. If you have medium-size speakers, 100Hz is usually about right. If they're really small, you might need 120Hz.

Once you do that, bass signals that are sent to any speaker below the programmed cutoff are sent to the sub instead.

Ahhhhh! Awesome, thanks for the help Malor. You gave me information that an hour of google searching failed to reveal. Your tip, combined with disabling 'full-range speakers' in the Speaker Setup in Windows 7 produced the desired results.