I selected a section which had 1-5 sec gaps between music. I used Effect/Truncate Silence/30,1,1,-40 - the gaps were still there. Does this feature work? I read the manual but was still unable to remove the gaps.
Yes the feature does work.
Perhaps the gaps have a background noise level above -40 dB? Try setting the “Threshold for Silence” to, say -20 dB and see what happens.
Thanks Steve. It works.
Steve what happened to my recording issue. I sent you 2 samples. Did you get a chance to hear them?
Do you mean this topic? https://forum.audacityteam.org/t/stereo-mix-missing-from-dell-win7-64/31128/1
Yes. Still cannot find the solution getting a good recording on my laptop.
Then don’t. Download the YouTube video instead 
Or ask your computer manufacturer for a new USB sound card.
Or try something like http://www.fxsound.com/dfx/ . Actually, the lack of an EQ on the built-in sound card would be very good reason for insisting on a replacement.
Gale