Hello Chris, thanks for your response. Eureka!! You solved my problem.
The solution was not to open Debut as admin but the selection of only speakers using MMDevice (no mic selected) was the solution.
I recorded music video's. in some different formats: fast capture, normal capture, avi, and mp4. All were recorded and played back with the sound.
I already did remove Debut from the pc when i got your message. Before your response, I spent many hours to find the solution.
In the forum i did not find anybody who reported that missing sound problems were solved by any suggestions.
I also informed NCH Technical support. But no response yet.
When i got your response i re-installed Debut and it turned out that your suggesttions are Bull's-eye for the windows 10 64 bit, Debut version 4.04.
Just for info: in the meantime i "play with" try-out an alternave freeware screen capture app called Flashback Recording https://www.flashbackrecorder.com/
Chris Many thanks and best regards
Peter Vestjens
The Netherlands