Windows Product Key for Installation

Hello,

I've used Parallels 3 and 4 in the past, but since I recently bought a new Macbook Pro, I went ahead and purchased Parallels 5. The installation went fine, but when I go to create a new virtual machine, it asks me for a Windows Product Key. I've never needed a product key when setting up my previous versions of Parallels. Do I need to purchase this, or I am just not setting this up correctly?

Thanks,
Kristin