There is a dual option, install Windows 7 (only can do 7) into Bootcamp, then install VMFusion or Parallels (payware virtual machine software) and it can copy the Bootcamp partition into a Windows virtual machine file in OS X.
This way you use Bootcamp Windows for the hardware performance needs only, keep if offline (except for updates) install the free Microsoft Security Essentials it should remain relatively clean. No files in, no surfing or email, it should stay almost virgin.
With the VM Windows you save a snapshot of the first copied Bootcamped version, then use a copy and use that online, only updating or installing software onto a reverted earleir version..
Anytime you get malware you can revert back to one of the snapshots. I maintain 3-4 versions of each Windows version myself, so I can go back months or years at a time, before the malware struck. Some are very sneaky and take a long time to discover.
Also I run XP, Vista, Win 7, Win 8 and various Linux versions all in VM's.