• What is SndControl?

Like Apple's Sound  control panel, SndControl allows you to change the sound your Mac utters whenever it needs to beep at you (aka the "alert" sound).

Unlike Apple's Sound, SndControl also allows you assign sounds to well over 30 distinct events, instead of just the beep. 
Most of the events can be assigned a sound by using the Control Panel, while one (having a specific sound played whenever a given application is launched) requires using Sound Mover, the companion program to SndControl in the Sound Manager Package.

NB:
Once you install SndControl (by simply dragging it to your System Folder), it takes over from Sound. 
If your Mac comes with a microphone, be sure to keep Sound  so you can record new sounds. If it doesn't, there's not much point keeping Sound on your hard disk.