<< XP will play DVD's for free natively. >>
No it won't. You either need a WORKING decoder installed (i.e., one that works correctly with its own player program, like PowerDVD 4.0 or WinDVD 3.0) or you need a "DVD Pack" specifically for XP from one of the major software DVD player vendors. Those all cost $14.99, coincidentally. PowerDVD is cheaper than that from Newegg.