Once you've formatted your HD, what are you installing to enable you PC to boot up. If its the reinstall software that came with a new PC, you could get some specific advice from the supplier, especially if its still in warranty. Also, why did you format your HD in the first place. Presumably it was because you had a problem? What was that problem, perhaps you have a hardware fault. Please provide a more detailed history and we may be able to take it from there.