[2008] Button border - would like transparent

I have a button on a form which has a picture as a background. I would like to remove the white square border from around the button or make it transparent so the background image is seen with rounded corners on the button (blue line being the edge of the button). Screen shot of the right side of the button is attached.

I have the BackColor property set to Transparent, Background Image is none, FlatAppearance BorderSize is 0, FlatStyle is Standard, Padding is 0,0,0,0. The FlatAppearance BorderColor must be a color, using the transparent setting (Web) is not valid.

Are there any settings that control this border to make it transparent, or make the button display with rounded corners?

Thanks

make an ownerdrawn button, consisting of an image with a border drawn around it. its a bit more work but its worth it

Can you please elaborate - is this a drawing done in VB or an imported graphic?