I own a Macbook (hence the title), i want to divide the hard-drive into 2 so 1 half is Windows, but i have 2 questions for you to answer.

1) I mostly want to use the Windows side for windows games, but how much of my 128GB hard drive should I give to the Windows partition?

2) What would be best, Windows XP or Windows Vista? (also include, for e.g Vista Premium and so on...)