>When adding a bitmap on a form, what determines the transparent backcolor that will not be shown when the image is used on a button? I have a bitmap which is having a white background. That color does not show in the button. How should we handle that?

Michel,

You probably know that you need an MSK file of the bitmap with the colored areas you wish in black. What the background color is depends on the bitmap. IOW, all areas of the rectangle are colored.