It's either a corrupt or a dead hard drive A good way to find out is to get an adapter so you can plug it trough the usb of another computer. If the other computer doesn't see it or anything this mean you got a dead hard drive. If you are lucky and you found your files back there is programs that can help you get you data back. If you don't care about your data you can just boot your computer with a windows cd, delete the old partition and reinstall windows
