Thanks for the idea, but it's not the recording program that's the problem. I've tried a handful of recording programs, even Microsoft's own built-in Recorder (located in Accessories), but none of the software hears or records anything. It's all a huge mystery, and I despair of fixing it without taking it into a repair shop. It's weird that everything was working fine on my system for years until recently. I've got a wonderful collection of mp3 files that I've recorded from the online Naxos library. So it's not that my sound card doesn't have a What You Hear feature, as I've seen suggested on elsewhere.
I've been looking around the Internet for other ideas and found lengthy discussions at
www.sevenforums.com, where all kinds of suggestions are given, but none of them apply to my case or, if they do, none of them have worked for me. I guess it's going to cost me some money to take it in to the shop, unless somebody here has had the same experience as me and actually knows for sure what's going on.