Turn volume up over 100% in Windows 7

Check the Control Panel of the Audio Software to see if you have some loudness protection checked.

Control Panel > Sound > Speakers, Properties > Enhancements = (in the scroll down menu) Loudness Equalization, deselect if needed.

I suppose you're talking about a laptop with built-in speakers.

I'm afraid there isn't much you can do, unless the driver/software for your sound chip provides such a feature (e.g. Realtek's Control Panel/Equalizer).

Some media players can boost the volume (e.g. VLC up to 400%) but that wouldn't help you to increase the volume for a certain application.

Other than that, get a set of speakers with decent amplification, also the sound quality will improve.

Try DFX audio enhancer - it did the trick

There is a program called Audio Hijack for the Mac that works great for this. I have not found a similar software program for the PC. But this hidden solution did work for me:

1. Open Control Panel
2. Open Sound
3. In the playback tab select Speakers
4. Click on Properties
5. Click on the Enhancements tab
6. Select the Equalizer
7. Next to the setting drop down list click on the "..." button to create your custom setting
8. Move all 10 bars in the equalizer to the max level
9. Click on Save, and give it a name like MaxMaxMax
10. Make sure the equalizer is check marked on in the Enhancements tab (it should be already)
11. You are super awesome! You win!

I had the same problem with using headphones with my laptop. I fixed it by buying one of those cheapo USB soundcards, like this (Link) :

Now, my headphones can blast out ear-bleeding sounds even before it reaches 100% volume.