Your Windows is installed in legacy BIOS mode. If openSUSE is indeed installed in UEFI mode it will not add Windows to boot menu, because you cannot boot legacy Windows bootloader in UEFI. Your best bet is to reinstall openSUSE in legacy BIOS mode.
Well legacy will only support 2 TB drives. GDI supports much larger. UEFI supports secure boot but only needed for Windows 8+ if you want it. Other then that no differences that mean anything. UEFI is much more complicated and thus has more problems being setup. As you can see lol
I’ve reinstalled and this time using GRUB2. The problem persists but in a different form. When powered on the system boots into Windows straight away, no GRUB. If I pull the boot menu on start up I can these options:
If I select HDD2 I get brought to GRUB (which is now giving an option to boot Windows), If I choose “opensuse” Windows starts. No problem I thought: “I’ll just change the boot order”. When changing the boot order in the BIOS, however, I’m only given 3 options: 1, 2 and 4.
Obviously I can’t just use “opensuse” since that boots Windows.
It’s not a huge issue I just don’t want to have to spam F12 every time I boot!
If you can’t change boot order in BIOS you can install grub into MBR of the first drive. Go into YaST2 bootloader configuration and select /dev/sda as bootloader location. This means you will no more be able to directly boot Windows unless you repair bootsector using Windows recovery tools.
# Modified by YaST2. Last modification on Thu May 9 00:04:55 BST 2013
# THIS FILE WILL BE PARTIALLY OVERWRITTEN by perl-Bootloader
# For the new kernel it try to figure out old parameters. In case we are not able to recognize it (e.g. change of flavor or strange install order ) it it use as fallback installation parameters from /etc/sysconfig/bootloader
###Don't change this comment - YaST2 identifier: Original name: linux###
title Desktop -- openSUSE 12.3 - 3.7.10-1.1
kernel /boot/vmlinuz-3.7.10-1.1-desktop root=/dev/disk/by-id/ata-WDC_WD1001FALS-403AA0_WD-WMATR0061169-part2 resume=/dev/disk/by-id/ata-WDC_WD1001FALS-403AA0_WD-WMATR0061169-part1 splash=silent quiet showopts
###Don't change this comment - YaST2 identifier: Original name: failsafe###
title Failsafe -- openSUSE 12.3 - 3.7.10-1.1
kernel /boot/vmlinuz-3.7.10-1.1-desktop root=/dev/disk/by-id/ata-WDC_WD1001FALS-403AA0_WD-WMATR0061169-part2 showopts apm=off noresume edd=off powersaved=off nohz=off highres=off processor.max_cstate=1 nomodeset x11failsafe
###Don't change this comment - YaST2 identifier: Original name: windows###