Theoretically, once you create the new partition for Windows with Boot camp, if you make it UNDER 32 GB! and after you install the OS and crap, you SHOULD be able to just move everything from the parallels drive to the one you just created, and then kill the parallels drive, which should then merge back with the mac drive.
I don't know if parallels lets you transfer files between disk partitions that easily, though. You might have to use flash drives or DVD-RWs or something.
but no, boot camp ALWAYS makes you create and format a NEW partition
but if you're talking about using both boot camp AND parallels at the same time, I doubt it would work. And it's also kinda pointless. It takes, like, 2 minutes to switch between the 2 with boot camp.