This problem is familiar with many HP notebook users, up to my knowledge you please don't afraid about your hard disk. The problem is not related to it. This error occurs approximately one year after you bought the notebook. When you press F10 button it displays BIOS window, then you press F10 again, a pop up appears displaying "Exit saving changes YES or NO". When you press YES then the system will restart automatically. If it again shows the error message no surprise at all, kindly repeat the above procedure for 4 to 5 times, accidentally and luckily your system will boot properly.