Question Missing second windows

[r.lichtenstein]

Hello,
I have second windows in another partition on the HDD, which by itself started to display on 'choose an operating system' / boot menu. Replacing the first windows - I had to format and install another Windows over it. Doing so, lost access to the second windows, no boot menu being displayed, cannot get into 'choose an operation system' in the advanced startup.

Was second OS (on second partition) somehow linked and dependent on the first OS? Is there any way to boot into the second OS?

Edit: Later, marked the second os partition as active, which was bad idea of course. After realizing first OS partition is also inaccessible now, formatted the (first) partition. Rebooted, still no OS displayed on the second partition.

 

[Ralston18]

What you are trying to do is referred to as "Dual Boot".

Not sure what process or procedure you have used to set it all up.

Here is a Microsoft link that should help:

https://answers.microsoft.com/en-us...ual-boot/2ba8750b-1d04-4a4d-980b-dbfb5bd6ef51

 

[r.lichtenstein]

What you are trying to do is referred to as "Dual Boot".

Not sure what process or procedure you have used to set it all up.

Forgot to mention, booting into both windows was a success, and had been using for over half a year or so. The problem isn't how to dual boot, rather, what happened to the second windows boot.

On HDD, I had windows 10 installed and running. Then decided to install another windows on the that hdd, created partition, and created bootable usb. While booting from USB, selected the newly created empty partition for installing windows. I have been using this technique before I even knew anything about dual boot. The 'Select operating system' menu at boot, occurred unintentionally. I guess this is another way to dual boot.

Edit: The problem is, recently I installed another windows over the very first windows - formatted & clean install. This is how I lost the second windows selectin option, as the OS selecting boot menu does not appear anymore. And OS partitions in the same HDD, do not show individually in bios. The second partition with OS is still there.