Help with MenuItem template.

Hey community

I tried to make a little modified GUI with "Expression Blend". I wanted to add a menu to it but it had that little white border around it which didnt fit with the other elements on the GUI.

Screenshot of the border:
http://imageshack.us/photo/my-images...icture1xs.png/

Screenshot of the hierachy:
http://imageshack.us/photo/my-images...icture2mh.png/

I have no idea how I can remove this border. I read that you need to change a default template but I have no idea where to do so.

Please help me :D