Windows – How to install a second Windows install on computer (on HDD2), but avoid the boot configuration of HDD1 to be modified

boothard drivepartitioningwindowswindows 7

I had:

Internal HDD1
Partition 1 100 MB: empty
Partition 2 150 GB: Windows 7 (BitLocker encrypted)
Partition 3 300 MB: BOOT 
Partition 4 700 GB: Data (BitLocker encrypted)

Internal HDD2
Empty

Then I installed Windows 10 on HDD2 with a classical USB flash drive Windows 10 installer (coming from official ISO), but I noticed it modified the boot partition of … HDD1!

i.e. if I remove HDD2 from computer, I still see a Windows 10 bootmenu when booting on HDD1 ; this confirms this installation has modified HDD1 too.

Question: How to install Windows 10 to HDD2 of a computer, without modifying anything (especially not the boot sector / boot menu / boot partition) on HDD1?

(Then you might ask: how would I boot on HDD2's Windows 10 then? I would like to do this rarely, but with the BIOS boot menu: F12: Boot on device: HDD2)

Best Answer

The easiest way to do it is to unplug HDD1 during Windows 10 installation.

Alternatively, you can use EasyBCD from Windows 10 to change your boot partition as described here, and then remove Windows 7 boot entries from Windows 10 and, vice versa, Windows 10 boot entries from Windows 7, using the same utility as described here.

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