I'm trying to make dual boot (Ubuntu server and Windows 7), installed on separated hard drives. But GRUB don't recognize Windows 7 boot. I've tried "sudo grub-update" along with "sudo os-prober". The "os-prober" finds the Windows 7, but when I update GRUB configuration, the Windows entry don't show up. I've tried so hard to find a solution, but I can't find one.