Remove Windows From Bootcamp

I am currently using a Macbook, 13-inch, late 2009, running Mac OS X Lion (originally purchased with OSX 10.6.0 Snow Leopard).

When I bought my Macbook, the drive had been partitioned with Bootcamp, so there are currently three drives; Macintosh HD, DATA, and Bootcamp. The Bootcamp drive runs Windows XP, which I no longer want, because I don't use it and it wastes a lot of space.

How would I go about removing the Windows from the Bootcamp partition, and if I do remove it, will that space be available as Macintosh HD space?

 

I have tried doing that, but when I open Bootcamp Assistant, it says that "the startup disk cannot be partitioned or restored to a single partition. The startup disk must be formatted as a single Mac OS Extended (Journaled) volume or already partitioned by Boot Camp Assistant for installing Windows."

I opened Disk Utility, and it is formatted as a single Mac OS Extended (Journaled) volume, and partitioned by Bootcamp Assistant.

When I click OK, it stays on the screen saying to download Windows Support Software.