Master Bus

I just got Movie Studio 15 Platinum and I am getting everything setup the way I like it.

One the Right Hand Side of the screen is a Audio Slider a Master Bus it is called.

I want to set the Slider in the middle.
I try to Drag the Slider to set the Volume in the middle but it wont move.

So I see a Pad Lock on the Bottom Left Side of the Master Bus and I click it.

Now my Mouse can move all over but I can not click on any Menus or anything.

The program Locks up but not the Mouse.

So I Reset the program to Default.

Does anyone know how I can Ajust my Master Bus?

I do go into Option then Audio and I see Audio Device.
And I have a Dropdown Box and it says.1. Microsoft Sound Mapper. 2. Direct Sound Surround Mapper. 3. Windows Clasic WAV Driver.

Can this be what is going on?
Witch one of these is the Right one?

I have Win7. 64 Bit.