I am considering switching to the Apple MacBook and I want to know some stuff about a Mac before that time, which will be sometime in June 2008. First question: Can you run Windows XP or Vista and take over the hard drive completely without the need for having OS X also?

nah - you need OSX as well (i think bootcamp (the thing that lets you install windows) runs under OSX)
i knew someone who tried installing XP over the top of everything and he b*ggered up his mac :|