Jeff is making the switch to Mac and he's going to need to use both Windows and Mac for a while. Leo says that there's a few ways to skin that cat including running Windows with Boot Camp, where you'll get to choose between Windows and OS X at boot up. You'll need your own copy of Windows, but it works really well. The second option is to run Windows virtually inside of OS X, and that way, you can just have a little sandboxed Windows window and what's good about that is that you have several options including Virtual Box, Parallels, and VMWare Fusion. Leo uses Fusion and it has this nice feature called "Coherence mode," which allows you to just run Windows for the application you need, without loading the entire OS virtually. It's pretty clever.