To Vlad:
Thank You for you suggestion. However I followed your instructions, but still no sound. However, as there was no ' HD Audio Rear Input device' I selected 'Realtek HD audio input' as shown on the attachment. I noted when I selected this device for Recording, I was presented with Recording Control, CD Volume, Mic Volume, Line Volume and Stereo Mix. All these boxes were checked. Howerer, the volume control under 'Recording' is the only control with green either end of the control slide and it is the only slide that works. All the other volume slides for CD Volume, Mic Volume, Line Volume and Stereo Mix do not have green either side of the volume control and will not slide. It is like drop down menus that are grey and inactive. The check box 'Mute' tick does work for them all.
Again, all other software sound and audio works for all other programs except 'Screen Capture' of AVS Video Editor.
I still need advice
Regards
Paul