You can use Disk Management to view and map disks and partitions (alternatively use diskpart.exe).
Usually first disk (disk 0) is boot candidate and checked for presence of active partition. If no active partition present on first disk, second disk (disk 1) is checked for active partition and so on.
Strange but device of is also listed as "unknown" in current system BCD! This could create problems.
A.) The best you can do would be rewriting MBR and PBR on all disks and partitions using bootsect.exe command:
bootsect /nt60 all /mbr
B.) Then use bcdboot.exe command to rewrite(fix) BCD:
bcdboot Z:\windows
where Z: is drive where Windows is installed. Later you have to fix recovery loader using ReAgentC.exe.
C.) You could write another BCD on non-system disk too (if it has an active partition) using
bcdboot z:\windows /s y:
where y: is active partition on non-system disk.
This way you can boot from either disk.
For viewing BCD in a graphical and structured way you could use Visual BCD Editor.
After executing bcdboot command you should check that devices for boot manager and loader are listed correctly.
After fixing BCD and reboot you can delete all loaders which have a "unknown" device, loaders pointing to partitions which are not the "boot" partition(where Windows is installed and started from).
Note:
Backup your current BCD(!) either using Visual BCD Editor or using
bcdedit /export full_path_filename
(you can restore BCD at any moment using "bcdedit /import filename")
All "links" in BCD are through GUIDs. For example element "display order" is a list of GUIDs which are GUIDs of loaders. Every object in BCD has a GUID which is unique.
Hope this helps.