I have been struggling finding a way to boost the volume of my laptop which has Windows 7 installed. Finally, the below stuff did the trick for me. Hope this helps!
1. Go to Control Panel -> Sounds
2. Select the Playback device and click Properties
3. Go to Enhancements tab and uncheck Loudness Equalization check box.
That’s it. It boosted the volume to a good extent for me. Hope this works for you too