windows xp restart after sp3 install-endless loop

Hi
I just try to install SP3 on my windows XP and after that my computer is not starting. I am now using window my friend's computer. My friend says that only solution is to format and reinstall window but I don't want to loose my programs. I do not want to do it all over again.

Can it be solved without format ?

Similar problem was posted earlier, solution is either install latest SP3 or follow the steps I gave here :
Win xP sp3 windows restart