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

I've installed Win10 on SSD (which goes straight to motherboard) and I have an old system on SSD which is 2,5" (?) which I connect to motherboard 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.

edit: Oh forgot, BIOS only gives this drive as an option too (besides usb, cd-rom and such external means...)




:)

 

Error: "An operating system wasn't found. Try disconnecting any drives that don't contain an operating system"

Hi Stephen,

I realize the inconvenience you are facing in accessing the operating system. Now that you have me with you let me take care of this.

Do let us know if you are able to see Windows 7/ Windows 10 operating system while rebooting the device?

As you are unable to boot the operating system, this issue might have occurred when the boot files are missing or corrupted.

I suggest you re-built the boot rec by following the below commands and check if it helps.
You will have to use Windows 10/7 installation media to follow the steps to boot into Recovery Environment and try to rebuild BCD.

Step 1: I suggest you to create an installation media for
operating system using the media creation tool

If system boots to Windows 10:
Installing Windows 10 using the media creation tool

If system boots to Windows 7: Download Windows 7 Disc Images (ISO Files)

Step 2: After preparing the installation media, insert it hard reboot the device and follow the below:

• Boot into Windows Recovery Environment using the Windows 10/7 installation media.
• Click on Repair your computer.
  
• Click on Troubleshoot and in the Advanced options.
• Select Command Prompt. Type the following commands into the prompt and press Enter key after each command.

• bootrec /fixmbr

• 
  bootrec /fixboot
  
• 
  bootrec /scanos
  
• 
  bootrec /rebuildbcd
  

5. Restart the computer.

NOTE: Modifying BIOS/ complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting
from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.

Hope it helps. Reply to the post with an updated status of booting the operating system for further assistance.

Thank you.

 

Preserving old operating system

When installing Win 10 can the old operating system be preserved for a dual boot or if I decide to revert to the old operating system can it be restored?

 

Windows 10 operating system & boot drive on different drives...

Windows keeps installing boot drive and operating system onto different drives...

Is there any way of installing boot and operating system onto one hard drive without disconnecting all the other hard drives internally?

What are the pro's and con's of this configuration?

Can you move the boot drive onto system drive hdd? (no 3rd party methods please)