OK if the drive was RAIDed then there may be meta data on it somewhere that says this and confusing the software.
Only thing I know to do is to wipe the entire disk with a dd command since I don’t know where that metadata is set. But you would need to reinstall. Also it is unclear which disk so both need to be wiped if you don’t know their history.
I made the changes to /etc/grub.d/40_custom in kwrite and ran it in Konsole (root) here is the output:
grub2-mkconfig -o /boot/grub2/grub.cfgGenerating grub.cfg ...
Found theme: /boot/grub2/themes/openSUSE/theme.txt
Found linux image: /boot/vmlinuz-3.7.10-1.11-desktop
Found initrd image: /boot/initrd-3.7.10-1.11-desktop
Found linux image: /boot/vmlinuz-3.7.10-1.4-desktop
Found initrd image: /boot/initrd-3.7.10-1.4-desktop
ERROR: ddf1: wrong # of devices in RAID set "ddf1_nas1" [1/3] on /dev/sda
No volume groups found
The message comes from dmraid that is called by os-prober. The message is entirely cosmetic - if dmraid fails, os-prober simply assumes there is no dmraid devices, and you do not have any.
The question remains why os-prober does not detect existing Windows installation. It may be a bug is os-prober. To debug it further I need logs from os-prober invocation. Logs are written in /var/log/messages.
DDF has “anchor block” - it is the very last block of device. It should be enough to clear it. But as I said already this should not change anything w.r.t. Windows detection.