Installing Win x86 dual-boot on a PC with Win 10 x64

Zimmerbie · 12 Jan 2016

Hello, as the title says, I have a PC with win 10 x64 installed. It is a new PC with UEFI firmware and secure boot enabled, though I can disabled it very easily.

I want to installed Win 7 x86 (32bit) on a second hard drive and have it dual-boot config with the current Win 10. I know I have to disable secure boot for installing 32 bit, but Im concerned about the process of installing Win 7 AFTER the already installed Win 10.

How can I go about doing this without losing access to my Win 10?
I need to install win 7 for compatibility reasons.

Thanks.

NavyLCDR · 12 Jan 2016

This is how I would do it. Disconnect your Windows 10 HDD. Leave only the HDD drive that you want Windows 7 on connected. Do a clean install of Windows 7 to it after making the bios adjustments required. After that is done, up and running, reconnect the Windows 10 HDD back as the priority drive. Reset the bios back to Windows 10 settings. When the computer boots to the Windows 10 HDD, then from an elevated ("run as administrator") command prompt type:

bcdboot D:\Windows /d /addlast

Path in red will be whatever drive letter \Windows gets assigned to the Windows 7 by Windows 10. Then I would use Minitool Partition Wizard to delete all the extra partitions on the Windows 7 HDD and expand the OS partition to fill the entire drive (unless you want a separate data partition.)

Nipax · 13 Jan 2016

Zimmerbie said:

I want to installed Win 7 x86 (32bit) on a second hard drive

If you use UEFI mode, you will not be able to install 32-bit version of Windows.

edit: SOURCE: UEFI Firmware

While the PC is in UEFI mode, the Windows PE version must match the PC architecture. A PC in 64-bit UEFI firmware mode can only boot 64-bit versions of Windows PE. A PC in 32-bit UEFI firmware mode can only boot 32-bit versions of Windows PE. On PCs that support both UEFI mode and legacy BIOS mode, you may be able to run 32-bit Windows PE on a 64-bit PC by changing BIOS menu settings from “UEFI mode” to “BIOS mode”, assuming the manufacturer supports legacy BIOS mode.

cereberus · 13 Jan 2016

Nipax said:

If you use UEFI mode, you will not be able to install 32-bit version of Windows.

SOURCE: https://technet.microsoft.com/fi-fi/.../hh824898.aspx

While in UEFI mode, the Windows version must match the PC architecture. A 64-bit UEFI PC can only boot 64-bit versions of Windows. A 32-bit PC can only boot 32-bit versions of Windows. In some cases, while in legacy BIOS mode, you may be able to run 32-bit Windows on a 64-bit PC, assuming the manufacturer supports 32-bit legacy BIOS mode on the PC.

You can run 32bit on EUFI on a 64bit pc if pc supports eufi-csm.

Many tablets have 32bit eufi OS on a 64bit cpu.

Virtually all 64bit pcs will support 32bit in legacy bios mode (never seen one that does not).

In OPs case, setting pc up in legacy bios mode and installing both will almost certainly work.

Could try installing 32bit in eufi mode first.

Nipax · 13 Jan 2016

You will need to install both versions (32-bit and 64-bit) in Legacy BIOS mode.

cereberus said:

Could try installing 32bit in eufi mode first.

This does not work if you have a 64-bit UEFI firmware.

SOURCE: UEFI Firmware

While the PC is in UEFI mode, the Windows PE version must match the PC architecture. A PC in 64-bit UEFI firmware mode can only boot 64-bit versions of Windows PE. A PC in 32-bit UEFI firmware mode can only boot 32-bit versions of Windows PE. On PCs that support both UEFI mode and legacy BIOS mode, you may be able to run 32-bit Windows PE on a 64-bit PC by changing BIOS menu settings from “UEFI mode” to “BIOS mode”, assuming the manufacturer supports legacy BIOS mode.

cereberus · 13 Jan 2016

Nipax said:

You will need to install both versions (32-bit and 64-bit) in Legacy BIOS

This does not work if you have a 64-bit UEFI firmware.

SOURCE: UEFI Firmware

While the PC is in UEFI mode, the Windows PE version must match the PC architecture. A PC in 64-bit UEFI firmware mode can only boot 64-bit versions of Windows PE. A PC in 32-bit UEFI firmware mode can only boot 32-bit versions of Windows PE. On PCs that support both UEFI mode and legacy BIOS mode, you may be able to run 32-bit Windows PE on a 64-bit PC by changing BIOS menu settings from “UEFI mode” to “BIOS mode”, assuming the manufacturer supports legacy BIOS mode.

Sorry - when I said try - no real expectation of it working. As you say, it is very firmware dependent.

I can only install 32bit eufi on my tablet (canot do legacy bios).

As we both said 'use legacy bios'.

Actually, a better solution could be to simply install the 32 bit version inside a virtual machine which will work on a 64bit pc.

Zimmerbie · 13 Jan 2016

Thanks for the rapid response guys, I have a ASUS Z170-A Motherboard, the newer generation skylake platforms, I have an option for CSM and disabling secureboot so I will see what happens. Installing it tonight!

DeaconFrost · 13 Jan 2016

Why not virtualize the other OSes and skip all of these steps and potential issues with your main, host OS?

Zimmerbie · 13 Jan 2016

NavyLCDR said:

This is how I would do it. Disconnect your Windows 10 HDD. Leave only the HDD drive that you want Windows 7 on connected. Do a clean install of Windows 7 to it after making the bios adjustments required. After that is done, up and running, reconnect the Windows 10 HDD back as the priority drive. Reset the bios back to Windows 10 settings. When the computer boots to the Windows 10 HDD, then from an elevated ("run as administrator") command prompt type:

bcdboot D:\Windows /d /addlast

Path in red will be whatever drive letter \Windows gets assigned to the Windows 7 by Windows 10. Then I would use Minitool Partition Wizard to delete all the extra partitions on the Windows 7 HDD and expand the OS partition to fill the entire drive (unless you want a separate data partition.)

Hey so I have installed Win 7 successfully, can still boot into Win 10, but I can seem to execute the command mentioned. It says error "failure to copy boot files". I am running on cmd as admin

DeaconFrost said:

Why not virtualize the other OSes and skip all of these steps and potential issues with your main, host OS?

I find Virtual OSes slow, and buggy, I need full hardware utilization without overhead

Berk · 13 Jan 2016

Zimmerbie said:

...Im concerned about the process of installing Win 7 AFTER the already installed Win 10...

I may be too late here, but I happen to have installed fresh copies of 10 & 7 on clean disk a few days ago. Albeit my Win 7 is 64 bit, but it's all UEFI.

I followed the partition scheme laid down by Windows 10: recovery|efi|msr|windows10|windows7

Installing 10 first, then 7 is/was as smooth a process as you could hope for! I ended up with the legacy bootloader automatically configured correctly by Windows and both OSs booting correctly. Both OSs installed via booting from their respective USB sticks (bootable 7 installer for UEFI made using Rufus)

N.B. for anyone wondering, the Mint 17.3 I run is installed on a separate disk with its' own EFI bootloader. I keep it disconnected while installing Windows and then use Grub Customizer to automatically detect Windows and set up the chain bootloader. Easy :)