Formatting as a Single OSX Volume [Removing Ubuntu Partition]

Hello everyone.

First off, I hope I put this in the right spot as I assumed this is the best place for Boot Camp help.

Now, I set up a partition to run Ubuntu on my MacBook, but now I want to remove that partition to make room for Windows XP. When I go to Boot Camp Assistant, I try to click 'Continue' but it gives me this:



I thought I could fix the problem using Disk Utility, but I couldn't understand what I could do. I thought it would work by erasing them, but I may have made the problem worse.

Here is what it looks like:



I tried booting the Ubuntu disc as I read I could remove the partition using that, but I don't understand how that would work.

Thank you for any help and sorry for the burden.