I have Ubuntu 12.04 LTS 64bit installed on one hard drive and Windows 7 installed on another hard drive. I can boot into each find when only one hard drive is plugged in. With both plugged in and in Ubuntu, running update-grub does not find the Windows 7 installation. With Both hard drives plugged in I cannot boot windows. The motherboard is an MSI 990XA-GD55.
I had installed Ubuntu first. Unplugged the Ubuntu drive to install windows to avoid overwriting the MBR (assuming windows still does that these days).
I think that windows only boots when the EFI boot option is selected in the BIOS, whereas usually the hard drive is specified. Have I somehow managed to install one as EFI and one as MBR? If so what does that actually mean, is this why grub cannot see the Windows installation? I would ideally have Windows as an option in the grub menu. Is this possible?