If you want to have two machines, that's fine. Let me give you an example of what I set up for my wife: She needs to use Windows for work. They have specialized applications that are Windows-only. She is also supposed to keep all of her work information confidential.
I bought her a MacBook Pro, and installed VMWare. With this software, she can run MS Windows as an application. When she switches to Windows, everything runs exactly like Windows, because it is Windows. She uses Windows strictly for work. All of her personal stuff: Pictures, web browsing, personal e-mail, etc is done using the Mac OS.
The advantage of this approach is that the Windows installation remains very lean, fast, uncluttered and secure. When you set up VMWare this way, you can share the Documents folder between Mac and Windows, so the see all of the same files. It is easy to set up and it works very well.