New
#11
What usually happens in a case where someone installs Windows on a PC that has another hard drive connected, and particularly when that other hard drive already has an Windows OS on it, is that the new installation will recognize that there is already an Active partition and it will use that instead of creating another one on the new hard drive. The reason for this is to preserve dual booting. So it is not a bug.
We have even seen cases here where the Active partition was installed on an extra blank hard drive.
That is why it is always recommended to disconnect all extra hard drives when clean installing an OS.
Don't forget to mark the old OS partition as Inactive:
Partition - Mark as Inactive