For MAXIMUM VOLUME, go to Control Panel, Sound (or Hardware + Sound, then Sound), and select Playback. Double-click “Speaker + Dual Headphones” and select Properties, then Advanced, and set the ‘Default Format’ drop-down menu to: 16 bit, 48,000 Hz (DVD quality). You can Test each of the different choices to make sure that’s the loudest.
Then, if you have RealTek HD Audio Manager (or equivalent), open it and click on Speakers, and follow on-screen directions to increase volume.
Once done, go to Control Panel + open IDT Audio, Playback, Select “Speakers and Dual Headphones.” Follow on-screen directions for Settings, Setup and Equalization.