Okay, I downloaded and installed all the latest drivers found at MSI & Realtek, still getting the same results. I couldn't figure out how to uninstall the drivers first, though; see below. But the downloads did their thing to no avail. The readme file said they uninstall first, reboot, and then install, but they went straight for the install.
I'm a newbie to 7 and am really finding it hard to get around in the system (the old axiom about old dogs & new tricks is quite true!). So bare with me if I'm poking around in all the wrong places. If I go under Control Panel - Hardware & Sound & click on the Sound tab, all it says is "No audio devices are installed", and all options are grayed out. Under the Owner-PC properties tab I see 4 entries for NVIDIA High Definition Audio, all which report functioning properly. Still, the x-ed out speaker icon remains in the tray saying No Audio Output Device is installed. Clicking that Icon does not help; troubleshooter can't find the problem.
I also ducked into BIOS setup just to make sure onboard sound hadn't been disabled somehow, but it was all hunky dory there.
Any other ideas?