I believe I seen the boot files while searching for the ones o needed to keep that said MBR....however the hard drive had windows 7 on it when I bought it from someone I worked with and at one time I am thinking they had windows 8.1 installed because when I got the windows 10 free update the computer started to offer me a choice of booting from the Windows 10 OS or Windows 8.1 OS....what is the possibility that there are 3 boot files because of the 3 different OS installed on it. (If windows 8.1 was indeed installed)?