Knowing that Windows was originally created to emulate the look and feel of the Mac, and that certain patents prevented a straightforward copy of will help you to understand just how keyboard shortcuts, buttons and sliders in the Mac desktop graphic user interface came to be the way they are, and why Windows is often the same but backwards, lol.
Seriously, though, if you’re coming from anything as recent as XP, there’s not a great deal of trauma involved and a lot to gain, such as not freaking out about whether to open that e-mail attachment or not.
bfl