Transparent background in icons Button Graphic

I have to make of controls Graphic Button with custom icons.
I'd like the background of these icons were transparent.

What characteristics or format must have the images used as icons for Graphic Button controls so that the background is transparent?

I tried the 16x16 PNG format that supports transparency, but acquire an ugly background (see attached file)

Hi, either you use ico files with transparent backgrounds (use TrueColor type in Microangelo and not Windows XP type) or you fill bmp files with the RGB-color 192,192,192. It is by design throughout Windows.

Regards, Fred

Thank you!
I solved creating the *.ico files  :)

I am not able to create ico file there are some file extension problems how can I deal with it?

I used:

{2}

Hallo

author=Emiliano link=topic=1791.msg8876#msg8876 date=1337275040 wrote:
I used:

{2}

With this software I created .ico file without any problems.  :)