Booting from a 2nd non bootable port

#1
Hello experts. I am in the middle of a very peculiar situation and I would appreciate any information or advice given.

My old HP pavilion laptop has an empty tray (SATA 2 port) for another HDD to install. In an attempt to revive the machine, I bought for it recently an internal SSD.

The plan is to dual boot Win10 from SSD on SATA 1 and Win7 from old HHD on SATA 2 (was on SATA 1).

Unfortunately, SATA 2 is not bootable like SATA 1.
The BIOS (Insyde f.1b) comes with many limitations for the advanced users, but I wouldn`t like to flash it. It`s only legacy mode, no UEFI, EFI or secure boot options to enable/disable.

OSs have been installed on each drive respectively and the machine boots itself always from SATA 1, while it sees SATA 2 only as storage space.

Tried a few other bootloaders to fix the MRB to no avail. They all see the second OS, Win7 on SATA 2, but none of them seems to work (Win10 on SSD was cloned from old HDD, which later got formatted to host Win7, I don`t believe that they still share the same MRB do they).

With that being said, Is it possible to enter the OS from SATA 2 with SATA 1 being the only bootable port? Can EasyBCD or some other bootloader application make this work?

Thanks in advance.
 

Terry60

Knows where his towel is.
Staff member
#2
On W10, add an entry for W7 in EasyBCD "Add an Entry" pointing at whatever disk letter W7 is seen by from W10 Explorer.
Click save, and that should be all you need.
Next time you boot W10, W7 should be an optiion in the boot menu.
You might then run into apparent problems which you'll find explained (and solved) here
https://neosmart.net/forums/showthread.php?t=12890
 
#3
Indeed Terry, you were correct.

EasyBCD did the trick and I can successfully boot in both OS now. I can't believe it was actually that simple. Thank you so much!!!

For reference, each OS prioritizes its drives first. When logged in with Win10, its local disk is referred as C: and Win7's is seen as H: (got other HP partitions also).
Similarly, when logged in with Win7, the previously C: drive has become H: and vice versa. Nothing to be bothered with.

Got one question though. Can the OSs recognize each other, or do they simply see the other OS as storage space?

I am asking because Win10 is basically an upgrade from my pre-installed Win7. I don't intend to use it, but it's still possible to revive my old Win7 from the HP recovery manager in the second drive. It would be nice to know if there will be any interference in case this happens.

Thank you again for your help.
 

Terry60

Knows where his towel is.
Staff member
#4
I too have W10 as a second OS, kept fully up to date with MS patches/upgrades, but never used.
It's an upgrade from W8.1 (which was a dog's breakfast of an OS) and similarly never used.
Just there for the time when W7 is dropped from support and I'm forced to use an OS full of gimicks I don't want and missing all the features I use all the time.
Disk letters are illusory, they don't exist in the real world, just in the registry of each individual Windows OS, so it's perfectly normal for your two OSs to see a completely different map of letters to partitions/devices.
Except in particular circumstances of custom installation techniques, the booted OS sees itself as C, hence any other OS cannot be C in its map because each letter association has to be unique in the registry table.
Letters don't actually exist in the BCD either. Partitions are identified by an unreadable (to humans) hash of the partitions's position on the drive and the unique serial number of the drive.
Because that would be extremely user-unfriendly in practice, EasyBCD translates the UID into a disk letter for your convenience, both when it communicates with you and in reverse when you give it instructions about where you want something. It uses the same registry table look-up as Explorer, so you'll notice the contents of the BCD apparently change depending on which OS you're using to look at it with.
The contents are actually unchanged, hence identical, but the translation into letters will reflect the world-view of the OS you are using to run EasyBCD.
Each OS just sees the other as just-another-partition, except for bootmgr of course and various repair/recovery programs.