If you want to have both Windows XP and the Mac on the same system, Parallels ($79) is the way to go. It's virtual machine software that runs Windows on top of the Mac OS, so that you can run most Windows applications on the Mac. It also supports Linux.
Parallels is a pretty amazing product -- nothing short of miraculous -- and yet I had such high expectations for it, based on many glowing reviews (including Richard Hoffman's article in InformationWeek), that I actually find myself a little disappointed with the reality.
I installed Parallels in about 10 minutes -- it's a straightforward Mac install. Then came the ritual Getting And Typing Of The Keys: You get your registration key for Parallels through e-mail, and you need a key even to run the evaluation. (The registration key from Microsoft was on a sticker attached to the CD, and is typed into the appropriate spot during the Windows install process. )
To test Parallels, I chose Windows XP Home Edition (based on reports that Vista is still problematic). Windows required about a half-hour to install; the process was nearly identical to a conventional Windows install.
Adding Coherence To Parallels
Until recently, when you ran Windows on Parallels, you ran Windows in its own window, and then ran your Windows applications inside the Windows window. You could also set Parallels up so that Windows took over your entire Mac desktop, with the Windows wallpaper and taskbar taking up the entire screen and replacing their Mac equivalents, leaving your Mac looking and acting like a PC.