High-pitched wavering noise

Using 2.x on Windows 7 on a PC, and Windows 8 on a laptop. Used the exe. installer. Same problem on both computers.
I have been using Audacity for two years with no problems, until last night. I’m getting a high-pitched wailing noise from Audacity on the PC, whether or not ION tape player is plugged in.
I installed Audacity 2.x on laptop for the first time, and I’m still getting the same noise.

Which Audacity exactly? You can get Audacity 2.1.0 from here.

http://audacityteam.org/download/windows

When it asks you to reset Preferences, say yes.

Don’t plug in any USB or external devices. Close Audacity.

Can you play a YouTube clip and does it sound OK?

Koz