Overwrite Mac OS with Windows 7

I recently won a MacBook AIR 11" 64GB laptop from a promo. I have always been a Windows user and I never had experience with Mac OS. I was wondering if I could format it and install Windows 7 over Mac OS. I don't want to use a virtual machine or Dual boot. I only want Windows running on it.
Is it possible to do so? Would there be harmful effects if I did?
