save BMP as 24 or 32 Bit

Question

hi I have a small problem I cannot solve: I m trying to save a Bitmap Object as a File - in this case as a *.bmp. This works fine, unfortunately the preset seems to save as a 32 Bit bmp with alpha channel. And many Programs like Combustion do only read 24 bit bmp's . But I didn't really get, how to save as a 24 bit image. Picture.Save(renderOutput, System.Drawing.Imaging.ImageFormat.Bmp); thats my code, can anyone explain to me those encoder parameters I have to set??? I would be very greatful! thanks a lot in advance maschka