With the MB or MBP, Windows doesn't recognize tapping the trackpad. So the double-tap which works in OS X won't help you. Also, you can't single-tap to replace clicking the trackpad button, either.
To right-click in WinXP, you can either ctrl+click or, using only the trackpad, press the trackpad button while touching the trackpad itself with TWO fingers simultaneously. In other words, it's like the two-finger click in OS X but you also have to press the trackpad button at the same time.