it will boot up with the xp2500 which is usually the big problem with boards of that age.
your limiting factor will be your memory speed.
here's a site that can help get the most out of your k7s5a and a xp2500.
http://p199.ezboard.com/bk7s5amotherboardforum
ud
>> Stay informed about: XP 2500 333 barton at 266