gtkrc and transparency

I searched for pixmaps on google, but found no site that would 
explain the format. Can anyone give me a link to a good pixmap 
information site or explain it to me?

Well, I was wondering on how to make a window transparent. I just 
want the window transparent, and not anything else like text and 
icons, because when you make text transparent you can't read it.

So the question is should I just make a transparent png file or is 
there a way to make a png/pixmap transparent from the gtkrc file? 
Also I searched the messages in this group for gtkrc and found a 
thread that said that gtk themes shouldn't be used on win32 because 
it would take up a lot of GDI. What is a GDI? And is the statement 
above true for the current version of GTK+?

- thanx, SUn