Hi,
If you run Win 10 it would probably be a Win 10 privacy issue for USB devices which we have experienced. However, since you are running Win 7 I would say it is most likely a driver issue. Both cameras use the same driver which will not work. Download the specific driver for Logitech QuickCam Easy and install that and test again.
Another way is to download Netcam Studio which is the next generation software after the webcam series. www.netcamstudio.com. Netcam Studio is free for two cameras. Install both USB cams there and test.
-Henrik