Windows 10: Old operatin system on other drive, how to boot it?

I've installed Win10 on SSD (which goes straight to emo) and I have an old system on SSD which is 2,5" (?) which I connect to emo with a cable, it's meant for laptops but never used anywhere but in my desktop. It had a working operating system but when I got a new SSD I decided to install Win10 there. Unrelated to the issue at hand I have an issue running a program correctly on this newer system, it's an audio recording software and for the life of me I cannot get the software to hear anything from line in. But the software is (and worked) on the old system so I'd like to boot that one (to get a small but important thing done) which is still intact, at least I haven't removed any system files from that drive.

How do I get Win10 to see that there is an alternative operating system on another drive?

I went to my computer --> properties ---> advanced system settings --> startup and recovery and pressed settings there. In the part where I can choose to have timer to select different systems I have the timer on but the drop box shows only this system as an option, hence no timer when booting. I'd need to somehow recover or awake the other system without messing with hardware (such as removing this active system disk, it's behind plenty of stuff I cannot dig out by my self). Also I shouldn't risk the status of this current operating system which is customized and running otherwise nicely so I'm weary of the though of running recovery/repair options on the older system, worrying that it might undermine the status of current operating system or messing up boot sectors all over the place, making this system unstable if I plug the other one physically out at some point (boot sectors crossed over multiple hard disks or something like that).

What might be going on here, why is the old system so undermined that I cannot get this windows to realize there is actually windows there too... It has two windows trees actually, windows and windows.old.

If it's relevant (and if I recall correctly) I installed my system on this new drive so that the old system drive was physically in place. What I *think* happened there was that the windows went to the new drive but boot sectors remained at the old drive. So I plugged the old drive completely out and then I managed to install this clean version completely from start (format c independent on this new drive. If that's the case then maybe it could be even the windows.old (on that other physical drive) I'd need to revive, again without risking harm this current one. However not sure if this is the case, keep in mind, it's been almost a year.

Any ideas are welcome

Thank you.




:)

 

Disk boot failure after removing old Vista partition

Thank you for the reply, muchomurka! As I indicated in my post, I have already tried all the steps you suggested to no avail:

- I cannot choose startup repair since the computer does not boot from the installation media
- I cannot use command prompt since the computer does not boot further than the POST screen
- I have disconnected and tried out all hard drives individually.

Since I had Win 10 up and running a few hours ago, I can say with 100% certainty that none of the hardware is faulty.

The real mystery is, how come the system won't boot from any media without an empty disk containing an old Vista boot sector being on top of the boot priority list? And which steps to take now that I've cleaned this disk and it does not exist anymore?

Would appreciate any ideas and pointers!

 

Boot from old hard drive

The motherboard of my old computer died suddenly and so I bought a new computer. It has two 1TB HDDs on RAID 0 and comes preinstalled with Windows 10 Home. I wanted my computer to boot from my old 120GB SSD from my old computer but it doesn't seem to recognize it as boot drive. It was working perfectly with my old computer.

I can view files from the SSD and so this confirms that it is working. The boot partition is marked active.

I tried changing the boot hard drive in the bios but in the bios, the only two options shown in the boot menu are

• Windows Boot Manager (Intel Volume1)
  
• CD/DVDRW
  

After searching online, a website suggested swapping the Sata of the old hard drive with that of the new one. I tried even this but this didn't work either. It gave me the error "boot disk not found" and in the boot menu, the only option was "CD/DVDRW".

For Reference :

Motherboard : ASUS Z170 PRO GAMING

All Hard Drives Run GPT.

Any other solutions?

 

Added SSD Drive for Windows only but desktop keeps booting from old HD

Yes it could be, but to check, user should disconnect his old drive then reboot. then if it boots to Windows 10, with no problems, he can go into his bios, and see if it now shows up correctly. I was just asking him to do some basic steps, for trouble shooting purposes.