It is possible to install Windows 7 to BIOS boot on your computer. Therefore, you could also install two Windows 7 operating systems in a dual boot configuration. Again, both would BIOS boot. I assume then that you could also upgrade the second Windows 7 to Windows 10. Again, Windows 10 would BIOS boot. When you boot the computer, a menu will appear which will allow you to select which windows you want to use. So you do not have to use a BIOS Windows 7 and UEFI Windows 10 combination.
The 64 bit Windows 10 installation media contains both the files to BIOS and UEFI boot. If you BIOS boot from the installation media, then the GUI will require the installation drive to be partitioned using the Master Boot Record (MBR) partition table. Windows will be installed to BIOS boot. Similarly, if you UEFI boot from the installation media, then the GUI will require the installation drive to be partitioned using the GUID Partition Table (GPT). Windows will be installed to UEFI boot.
You can also boot from the Windows 7 or 10 installation media, open a Command Prompt window, then issue commands to install Windows. This is one way to BIOS boot from the media, then install Windows to UEFI boot. The reverse is also true. (i.e. UEFI boot and BIOS install) However, installing from the command line is rarely needed.
Legacy Mac computers also allowed for hybrid partitioning where both the MBR partition table and GPT were used to install operating systems. In this case, you could install Windows to BIOS boot and also have other operating systems (such as macOS and Linux) UEFI boot. It is because of this that Windows 7 can not be installed to BIOS boot and have Windows 10 also installed to UEFI boot. In other words, once you setup a hybrid arrangement both Windows 7 and 10 have to be installed to BIOS boot.
Install a Dual Boot from a Command Prompt Window
A free product named VirtualBox was used to illustrate and test the procedure.
Here is how VirtualBox version 6.0.14 r133895 (Qt5.6.3) was setup. The Name, Type and Version where chosen as shown below.
Note: The host computer is an Apple iMac (21.5-inch, Mid 2011).
Since the host computer has 16 GB of memory, the virtual machine was set to have 4096 MB of Base Memory. Also, to EFI boot Enable EFI (special Ones only) was checked off. See below for an illustration.
Since the host has 4 cores, the Processor(s) was set to 2 CPUs. Also, Enable PAE/NX was checked off. See below for an illustration.
Finally, a second SATA internal drive was added, as shown below.
The current Windows 10 and Windows 7 iso files were downloaded from Microsoft. The iso files were virtually inserted in the virtual machine DVD drive starting with the Windows 10 iso. Physical iso files were used to install Windows. However, physical flash drives can be substituted without significantly changing the steps shown below.
After UEFI booting from the virtual DVD drive containing the Windows 10 iso, the following window was displayed.
Entering the key combination shift+F10 will open a Command Prompt window, as shown below.
The following commands were entered to install Windows 7 to BIOS boot on disk 0 and Windows 10 to UEFI boot on disk 1. Be aware, there is a comment where you need to swap the Windows 7 DVD for the Windows 10 DVD.
Note: In the commands shown below, you may have to substitute install.esd for install.wim.
Microsoft Windows [Version 10.0.18362.418]
(c) 2019 Microsoft Corporation. All rights reserved.
X:\Sources>diskpart
Microsoft DiskPart version 10.0.18362.1
Copyright (C) Microsoft Corporation.
On computer: MINWINPC
DISKPART> select disk 0
Disk 0 is now the selected disk.
DISKPART> clean
DiskPart succeeded in cleaning the disk.
DISKPART> create partition primary
DiskPart succeeded in creating the specified partition.
DISKPART> format fs=ntfs label=Windows7 quick
100 percent completed
DiskPart successfully formatted the volume.
DISKPART> active
DiskPart marked the current partition as active.
DISKPART> assign letter=c
DiskPart successfully assigned the drive letter or mount point.
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> clean
DiskPart succeeded in cleaning the disk.
DISKPART> convert gpt
DiskPart successfully converted the selected disk to GPT format.
DISKPART> create partition efi size=300
DiskPart succeeded in creating the specified partition.
DISKPART> format fs=fat32 label=EFI quick
100 percent completed
DiskPart successfully formatted the volume.
DISKPART> assign letter=s
DiskPart successfully assigned the drive letter or mount point.
DISKPART> create partition msr size=16
DiskPart succeeded in creating the specified partition.
DISKPART> create partition primary
DiskPart succeeded in creating the specified partition.
DISKPART> format fs=ntfs label=Windows10 quick
100 percent completed
DiskPart successfully formatted the volume.
DISKPART> assign letter=w
DiskPart successfully assigned the drive letter or mount point.
DISKPART> exit
Leaving DiskPart...
X:\Sources>dism /get-imageinfo /imagefile:d:\sources\install.wim
Deployment Image Servicing and Management tool
Version: 10.0.18362.1
Details for image : d:\sources\install.wim
Index : 1
Name : Windows 10 Home
Description : Windows 10 Home
Size : 14,513,453,277 bytes
Index : 2
Name : Windows 10 Home N
Description : Windows 10 Home N
Size : 13,698,165,844 bytes
Index : 3
Name : Windows 10 Home Single Language
Description : Windows 10 Home Single Language
Size : 14,495,067,516 bytes
Index : 4
Name : Windows 10 Education
Description : Windows 10 Education
Size : 14,780,689,298 bytes
Index : 5
Name : Windows 10 Education N
Description : Windows 10 Education N
Size : 13,967,235,459 bytes
Index : 6
Name : Windows 10 Pro
Description : Windows 10 Pro
Size : 14,782,181,615 bytes
Index : 7
Name : Windows 10 Pro N
Description : Windows 10 Pro N
Size : 13,968,715,159 bytes
Index : 8
Name : Windows 10 Pro Education
Description : Windows 10 Pro Education
Size : 14,780,619,060 bytes
Index : 9
Name : Windows 10 Pro Education N
Description : Windows 10 Pro Education N
Size : 13,967,164,321 bytes
Index : 10
Name : Windows 10 Pro for Workstations
Description : Windows 10 Pro for Workstations
Size : 14,780,653,945 bytes
Index : 11
Name : Windows 10 Pro N for Workstations
Description : Windows 10 Pro N for Workstations
Size : 13,967,199,656 bytes
The operation completed successfully.
X:\Sources>dism /apply-image /imagefile:d:\sources\install.wim /index:6 /applydir:w:\ /checkintegrity
Deployment Image Servicing and Management tool
Version: 10.0.18362.1
Applying image
[==========================100.0%==========================]
The operation completed successfully.
X:\Sources>rem Removed Windows 10 DVD and inserted Windows 7 DVD.
X:\Sources>dism /get-imageinfo /imagefile:d:\sources\install.wim
Deployment Image Servicing and Management tool
Version: 10.0.18362.1
Details for image : d:\sources\install.wim
Index : 1
Name : Windows 7 Home Basic
Description : Windows 7 Home Basic
Size : 11,710,161,360 bytes
Index : 2
Name : Windows 7 Home Premium
Description : Windows 7 Home Premium
Size : 12,222,587,449 bytes
Index : 3
Name : Windows 7 Professional
Description : Windows 7 Professional
Size : 12,122,886,417 bytes
Index : 4
Name : Windows 7 Ultimate
Description : Windows 7 Ultimate
Size : 12,285,492,779 bytes
The operation completed successfully.
X:\Sources>dism /apply-image /imagefile:d:\sources\install.wim /index:3 /applydir:c:\ /checkintegrity
Deployment Image Servicing and Management tool
Version: 10.0.18362.1
Applying image
[==========================100.0%==========================]
The operation completed successfully.
X:\Sources>bcdboot c:\windows /l en-us /s c: /f bios
Boot files successfully created.
X:\sources>bcdboot w:\windows /l en-us /s s: /f uefi
Boot files successfully created.
X:\sources>bootsect /nt60 c: /mbr
Target volumes will be updated with BOOTMGR compatible bootcode.
C: (\\?\Volume{02cca004-0000-0000-0000-100000000000})
Successfully updated NTFS filesystem bootcode.
\??\PhysicalDrive0
Successfully updated disk bootcode.
Bootcode was successfully updated on all targeted volumes.
X:\sources>exit
Remove the DVD and click on the the red X to restart the virtual machine. Finish installing Windows 10. Shutdown the virtual machine then uncheck the Enable EFI (special Ones only) option in the setup, as shown below.
BIOS boot the virtual machine and finish installing Windows 7.
Optional Steps
The following was omitted in the above example.
- The System and Recovery partitions were omitted from disk 0. The files that would have been stored in these partitions were installed in Windows partition of disk 0 instead.
- The Recovery partition was omitted from disk 1. The files that would have been stored in this partition were installed in Windows partition on disk 1 instead.
- Any extra steps needed to install for Secure Boot.
- The use of the
Dism /Add-Driver command to add any required drivers to the driver store.
Additional References
DISM Image Management Command-Line Options
DISM Driver Servicing (.inf) Command-Line Options
BCDBoot Command-Line Options
Bootsect Command-Line Options
BIOS/MBR-based hard drive partitions
UEFI/GPT-based hard drive partitions
