Please help me, Deleting windows partition

OK so a while ago I had installed Windows on my Mac book and i found out it was service pack one, so i now have service pack 2 and tried to delete the old partition through disk utilities and it has not deleted. I had then found out I could have deleted it through boot camp but since I had deleted most of the files through the utility and if I try and use boot camp it says "The startup disk must be formatted as a single Mac OS Extended (Journaled) volume or already partitioned by Boot Camp Assistant for installing Windows." So what do i need to do? Do I need to make the Windows partition OS X again? And if so how?
Please help me, Thank you so much.
Icotope,

Open Boot Camp Assistant in Applications => Utilities. It will prompt you to restore to a single partition. The rest is self-explanatory. Make sure you have a backup of your data before you start.