I switched my system over to the surround audio jacks built-in to my motherboard (4 stereo-to-rca cables going into my Yamaha stereo's 5-channel-input). In Linux, they were detected right away and work 100% correctly when I tested each of the 4 speakers and sub.
Rebooting in Windows 7, there is no sound.
The Playback Devices reads: Speakers
2-High Definition Audio Device
Not Plugged In
It also shows two HDMI devices, one of which is enabled. I don't even have HDMI ports on my PC! But that happens in Linux too, and I just select the "Analog 5-channel" outputs and all is well.
Since everything works fine under Linux, I know there are no problems with the connections or hardware or stereo settings. I can get Windows to recognize the 2-channel speakers if I move the cables, but I'd like to get the surround sound working.
Double click the speaker icon in the lower right hand of the desktop, this will bring up the mixer, or single click to bring up the volume control. Laptops: see below, third paragraph.
Check the setting of the mixer or volume control.
But in case the volume is missing, corrupted, or the audio is otherwise non-functional:
you check whichever audio was installed:
click start, click control panel, click add remove programs, look at the list...
which audio software is shown on the list? delete it, restart the computer.
now visit the motherboard manufacturer or computer manufacturer's website
look up your computer drivers by model number
download the latest audio drivers, save on the desktop...
turn the antivirus off,
if you have multiple security programs installed, turn them all off
(your driver may not install if security systems are turned on)
now load your new audio driver, restart, turn the antivirus back on.
Laptops: Your volume controls may be built into the keyboard. (varies according to make and model number)
OR: your volume control may be a knob, located near the headphone jack.
Download the entire manual for your computer model from the manufacturer's website.
The manual will show you where all the keyboard audio or wireless ethernet controls are located.
But besides the manufacturer keyboard controls, you will still have software controls, as above. (first paragraph)
So if "either one of these volume controls is turned to "zero" you will have no sound. If the Mixer is turned to zero, or muted, you will have no sound.
Hmmm, better check that.
Actually, the Realtek software automatically uninstalled the old driver, problem was that upon reboot, Windows automatically re-installed again.
Problem eventually solved by doing "update driver" and pointing it at downloaded driver files from Gateway website.
After some minor confusion with the front-LR speakers being in the wrong jack (Linux was forgiving, Windows was not; upon switching to Windows' preferred, Linux was still satisfied with channel arrangement), got everything working hunky-dory.