The problem you have is that the border is not part of your owner drawn menu. When a menu is popped up a window is created which has the border you need to remove. Handling the WM_MEASUREITEM / WM_DRAWITEM is not enough. THis only is used to set the size of the window and to draw onto it.

You need to hook the creation of this window and change its style. Isf you set a hook and catch WM_CREATE messages and loook for a window class of "#32768" you should be able at that point to set the border style so that the menu will not be shown with a border.

Also, remember that not all menus use the window class name of #32768, so you may find that you will have to check for other class names also.

I cant remeber the other class names that you would expect to see, but a search should turn them up for you.