|The Youtube clips aren't necessarily using the same sound output volume control in the mixer settings.|
It's npt likely your problem has anything to do with the Nero software itself .
However, this applies to all burning prgrams....
If you copied a disk with the software,
- use "disk at once" or similar to copy the entire contents of the disk, including files that may not be visible in Windows
- or - may not work for all disks (e.g. you must do the above for Windows disks) - make sure you have Control Panel - Folder Options - View set to show all Hidden and System files, which is NOT the default setting.
It's also possible you may need to install specific audio codecs