Increase volume on weak laptop speakers Windows 7

You can boost the sound by 200%

1.  Right click on "speak icon" on the right corner of the display
2.  Click "Playback devices"
3.  Under Playback Tab, click "Speaker -HD Audio Device" and then click "Properties"
4. Under Enhancements Tab, check on "Loudness Equalization", then click OK

The only con is that, there is more distortion at max volume. At 50-75% volume works fine
This option works great for headphones and external speakers too.