I have a 15" MacBookPro. Also have a Pfaff 2170 embroidery machine which 4D Embroidery software is not compatible with Snow Leopard or any of the operating systems. But my Mac came with Boot Camp. At the time my choice was install Windows XP on one side of Boot Camp, so that there would be dual processors.
The other choice was Parallels, which if basically the same but you can have both Snow Leopard and Boot Camp running at the same time. I didn't like that idea so I went with Boot Camp since it was already there.
When I turn on the Mac it defaults to the Mac side, but to get to Window XP I have to hold down the "Option" key until the gray screen with the two separate hard drive disk come up, and then I double click on the Window XP one to get to my Embroidery 4D software. I also download my designs and save them from my email purchases on that side. I do run a security program and it has indeed detected viruses from time to time and quarantined or deleted them. Never see any on the Mac side.
I hate having to have Windows on my Mac but that is the only way to transfer embroidery designs to my Pfaff without going out and bying a Dell or any other Windows supported system.