From company's website (https://www.indievolume.com)
IndieVolume is a per-application volume control for Windows XP.
IndieVolume makes Windows programs use separate volume controls independent of other Windows programs.
Bespoke per-application volume, IndieVolume can also make Windows programs shut when GPS speaks, boost too silent sound, propagate sounds to multiple rooms
in your apartment and many more.

Problems IndieVolume can solve:

Every application can have separate volume level, independent of other applications volume level.

For example, you are listening to the music, and suddenly some application LOUDLY shouts or dings — with IndieVolume you just configure shouting application
to sound at different (lower) volume compared with the volume at which player application is playing music.
Every application can be (forcibly) muted independent of other applications.

For example, you have occasionally visited one of that websites, that play horrible sounds in the background — using IndieVolume you can just mute web browser
not to output any sound at all. Or you like to play flash games and would like to control volume level — IndieVolume can do that as well.
Two or more soundcards, but applications play only on one.

For example, if you have built-in sound card and SoundBlaster as second sound card, or USB/Bluetooth headset, you can configure certain applications play
on built-in sound card, and others play on SoundBlaster or USB headset, fully employing your audio hardware. 

Mute all applications when critical application plays a sound.

For example, you are having business chat in Skype or GoogleTalk, and suddenly some application plays a sound — with IndieVolume, you can mark Skype/GoogleTalk
as "exclusive", so none application would sound during your Skype/GoogleTalk calls. 
Ugly sounds.

If you do not have SoundBlaster, you can enrich application sounds by applying fancy effects — IndieVolume comes preconfigured with over 50 FX presets,
similar to SoundBlaster ones; it is software replacement for SoundBlaster.

Prize: $24.95  

Instructions: Use serial provided (found inside serial.txt) to register.