Transparent Windows

I want to design a program that will launch a window that is constantly transparent but also above all other windows on the screen.

I can see how it may be possible to capture the portion of the screen below the window and then merge it with the pixels from the window. However, since this window will always be on top, even when it doesn't have focus, the items underneath could be changing pixels. I have seen some programs, like the one from trillian.cc, do a good job with transparency.

Does anyone know how I might accomplish this?
Oh yes, and I use old-style C programming for windows but with a c++ compiler ( visual c++ w/ visual studio.net interface ).

oh, Nevermind. I found a function called SetLayeredWindowAttributes that is supposes to set the transparency of the window through the os.

Only suppose to work for win2k and winxp tho.