OK, you Windows 10 people, if Audacity doesn't work for you, you may need to update your sound card drivers. Here's what you do:
At the bottom-left corner of your screen, next to the Windows/Start Menu icon, you should find a box that says Search the Web and Windows. Put device manager in the box, and a list should appear and you should click on (guess what?) device manager. Go down to Sound, video, and game controllers. Right-click on the one that looks like it's a sound card (mine says NVIDIA High Definition Audio, and also Realtek High Definition Audio, so I delete them both), and select "uninstall." Also check the box that says "delete the driver software for this device" (making sure you have a good Internet connection). Once you've clicked "OK" (with some trepidation), reboot your computer. The computer should then reinstall the sound card software, and quite likely it will work with Audacity.

This technique works quite well as a last-resort technique with most Windows driver problems, but I admit it's kinda scary to delete drivers for essential features of your computer. I can't say I'm over being scared, but the technique almost always works for me. If not, I go back to the last restore point on my computer, and try again.

-Joe-