How do I stop apple boot camp from defaulting to windows on startup?

I briefly used boot camp, but I decided to switch to parallels. Unfortunately, despite my deleting on the partition, when I start my computer it still tries to boot into windows, which since I deleted the partition leads to it saying: "please insert boot disk." I tried inserting my copy of windows and it didn't work. I even tried starting the computer wit the disk in and running the installer, but that didn't work either. How do I get it so that my computer boots automatically into OS X?