I have installed windows service pack2 but "pirated".?

I have installed windows service pack2 but "pirated".wat the problem is wen i try to update my xp.First it try to validate after this validation my sytem automatically get reinstalled ,after that when i switch on my sytem a Microsoft icon occur,it shows that "validate ur genuine copy of windows".i want to get rid of this wat i can do to solve this problem.