Problem with my PC

Hello, i have a p4 system in my home...but there is a problem with my motherboard...i do have my p3 system..i have connected my harddrive to this p3...before connecting to the system i have installed the XP by ghost(my college admin has done that for me) but when i have connected that to my p3 syatem it has not worked..again i have reinstalled winxP upon that...it has worked for many days...but now it has got some problem....when im installing XP...the blue screen appeared...it has asked to press f8 to agree after that it is getting restarted...i dont what is the problem with my system....please suggest me what to do....