Run Bootcamp Assistant again. It is located in your OSx Utilities Folder. Select the menu item to Intall or Remove Windows. Select Remove Bootcamp and return your hard drive to a single OSx partition.
Below is the paragraph from the instructions. Follow it exactly and then report what happens at each stage.
How you remove Windows from your computer depends on whether you installed
Windows on a second disk partition or on a single-volume disk.
If you installed Windows on a second disk partition: Using Boot Camp Assistant as
described below, remove Windows by deleting the Windows partition and restoring
the disk to a single-partition Mac OS X volume.
If your computer has multiple disks and you installed Windows on a disk that has only one
partition: Start up in Mac OS X and use Disk Utility, in the Utilities folder, to reformat it
as a Mac OS X volume.
To delete Windows and the Windows partition:
1 Start up in Mac OS X.
2 Quit all open applications and log out any other users on your computer.
3 Open Boot Camp Assistant.
4 Select “Remove Windows 7,” and then click Continue.
5 Do one of the following:
a If your computer has a single internal disk, click Restore.
b If your computer has multiple internal disks, select the disk with Windows on it,
and then select “Restore to a single Mac OS partition” and click Continue.
CampTune should get your partition back.
In the past, to reallocate free space on your Mac, you’d need to back up the Boot Camp partition, delete the partition, recreate an NTFS partition with a new size and, finally, restore the Windows partition backup to the new NTFS partition, a process that could take anywhere between two to five hours. Fortunately, Paragon Software has developed Camptune X, which achieves the same result in a matter of minutes!