Enjoy your iMac because it's a great machine. To use the calibration software all you need to do is get yourself a copy of VMWare Fusion and Windows 7Pro. Instsall that on your Mac and your good to go. Yes i made it seem very simple..lol it's not very difficult.
You basically you need to run Windows. Your options are to either run a VM like Fusion or Parallels (as noted above), or create a Windows partition on your HD and use Bootcamp mode.