my bot

hey guys I’m new to blender. So far seems cool , I’m working on my first project witch will be a vfx type test shot to sort of test out blender and what I can do with it. here is a rough first render with cycles. Can some one tell me how I can have an hdr image in the world environment so that it lights and reflects on my model but does not actually render into the image? I need an alpha of my robot so I can composite it. any info would really help thanks

http://www.lost-bot.com/wp-content/uploads/2012/02/blendRobotsmall.jpg

In the “Film” tab of the “Render” panel check the box labeled “transparent”.