Make sure you reseat the component such RAM, video card, power cable, and data cables (SATA and IDE). It will solve the problem however if not success, try reseat the CPU if suspected.
If your PC are new build, make sure the component are properly installed.
If your PC are old (or maybe no longer used), I'm not sure what causes it, but the POST diagnostic card can help you find the cause. If possible, replace some component (such RAM, video card, etc) if you suspect some component are dead.
I have checked all of my components(RAM,videocard,power cables,sata,harddisk),all are working fine on another pc.i checked my processor too.but i still don't get boot from my pc.Can i have question for u.Except these components which component is most likely doesn't work in my pc.By the way i ordered a new motherbord.