Did you install XP and then change the hardware?
I'm not certain but I think you will have to clean install after adding new motherboard processer?
Possibly also an incorect BOIS setting.
Yoy need tp press DEL during POST to enter setup, check BOIS settings with Motherboard manual.
F9 may be a boot menu (motherbord manual should tell you)
Any more info you have may be helpful