Desktop animation overlay (Like Winamp's Advance Visualization Tool) and alphablend

Question 1: Desktop Animation Overlay
If you've Winamp, try enabling the visualizer by pressing CTRL+K,
then select Advance Visualization Tool, and click start.
A new window should appear.
Double-click it would launch Winamp AVS Editor.
From the menu, Click Settings->Display.
There's this Overlay mode, enable it.
Check 'set desktop to color' as well.
You'd see that your desktop has this visualization animating on it.

I doubt it's using Active Desktop webpage, I checked it.
I just donno how it's done. Anyone knows?

Question 2: Alphablend
I've found some Alphablend APIs, it's working great on picturebox.
But I want to alphablend it on my desktop, just like Winamp's
Advance Visualization does.
I've try this by getting the Desktop's hDC through some APIs,
then alphablend my form's hDC with the Desktop's hDC, but it
never works.
Can anyone point me the right way?

Thanx :cool: