i have downloaded win7 onto a tumb drive along with an iso file from micrsoft store, then i copy the files onto a dvd when to boot from eigther one it won't go then i have 500 gb portble hard drive were i copy the files onto try to boot from it's still the same that return "BOOTMGR is missing" please help, am going nut with that, computer is a pc dell inspirion 620.