How to Remove and Uninstall Windows 7, 8, or 10 from Dual Boot PC Installation & Upgrade

Your Windows 7 partition is marked as active because that is the partition the computer is booting from. It was likely your first OS and you added Windows 10 to it. In order to reformat the Windows 7 partition you are going to need to make your Windows 10 the system partition the computer boots from. To do that, open a Command Prompt with Administrator privileges (run as administrator) and use the following commands:

Code:

diskpart
select vol c
active
exit
bcdboot C:\Windows /s C: /f BIOS
exit

Reboot the computer and your Windows 10 C: drive will be active and you can reformat the Windows 7 partition.

NavyLCDR said:

Code:

bcdboot C:\Windows /s C: /f BIOS
exit

Reboot the computer and your Windows 10 C: drive will be active and you can reformat the Windows 7 partition.

Thank you.
is that /s switch necessary? I read that the /s switch is used to configure the second hard drive or hard drive in diff computer. Currently, I just want to get rid of the Win7 partition and use only Windows 10 partition in this very same PC.

Yes, the /s is needed.

NavyLCDR said:

Yes, the /s is needed.

Ok.Done.
But something went wrong.dont know what....
My pc refused to start with error ntldr missing press ctrl+alt+delete.
What are my options now ??

Brink said:

Hello,

Try performing a Startup Repair below for Windows 10 to see if that may help allow it to boot again.

Run Startup Repair in Windows 10

Also on step 4 of the tutorial linked to by Brink, is the option to open a command prompt. In the boot folder of the Windows 10 USB flash drive is the command bootsect. You can use that command to put ntldr into the active partition on your hard drive:

Code:

bootsect /help

bootsect {/help|/nt60|/nt52} {SYS|ALL|<DriveLetter>:} [/force] [/mbr]

Boot sector restoration tool

Bootsect.exe updates the master boot code for hard disk partitions in order to
switch between BOOTMGR and NTLDR.  You can use this tool to restore the boot
sector on your computer.

/help   Displays these usage instructions.

/nt52   Applies the master boot code that is compatible with NTLDR to SYS,
        ALL, or <DriveLetter>.  The operating system installed on SYS, ALL, or
        <DriveLetter> must be older than Windows Vista.

/nt60   Applies the master boot code that is compatible with BOOTMGR to SYS,
        ALL, or <DriveLetter>.  The operating system installed on SYS, ALL, or
        <DriveLetter> must be Windows Vista, Windows Server 2008 or later.

SYS     Updates the master boot code on the system partition used to boot
        Windows.

ALL     Updates the master boot code on all partitions.  ALL does not
        necessarily update the boot code for each volume.  Instead, this
        option updates the boot code on volumes that could be used as Windows
        boot volumes, which excludes any dynamic volumes that are not
        connected with an underlying disk partition.  This restriction is
        present because boot code must be located at the beginning of a disk
        partition.

<DriveLetter> Updates the master boot code on the volume associated with this
        drive letter.  Boot code will not be updated if either 1)
        <DriveLetter> is not associated with a volume or 2) <DriveLetter> is
        associated with a volume not connected to an underlying disk
        partition.

/force  Forcibly dismounts the volume(s) during the boot code update.  You
        should use this option with caution.

        If Bootsect.exe cannot gain exclusive volume access then the file
        system may overwrite the boot code before the next reboot.
        Bootsect.exe always attempts to lock and dismount the volume before
        each update.  When /force is specified, a forced dismount is attempted
        if the initial lock attempt fails.  A lock can fail, for example, if
        files on the target volume are currently opened by other programs.

        When successful, a forced dismount allows exclusive volume access and
        a reliable boot code update even though the initial lock failed.  At
        the same time, a forced dismount invalidates all open handles to files
        on the target volume.  This could result in unexpected behavior from
        the programs that opened these files.  Therefore, you should use this
        option with caution.

/mbr    Updates the Master Boot Record without changing the partition table on
        sector 0 of the disk that contains the partition specified by SYS, ALL,
        or drive letter.  When used with /nt52 option, the master boot record
        is compatible with operating systems older than Windows Vista.  When
        used with the /nt60 option, the master boot record is compatible with
        Windows Vista, Windows Server 2008 or later.

Example:

To apply the master boot code that is compatible with NTLDR to the volume
labeled E:, use the following command:

bootsect /nt52 E:

Another alternative in command prompt would be to go back into diskpart and set the old Windows 7 partition as active again.

A third option would be to create a USB flash drive of Kyhi's Recovery Drive, boot into that and run Macrium Reflect. Under the restore menu of Macrium Reflect is a utility to fix Windows Boot Problems, you can run that utility and it will probably fix it.

Or a fourth option, which will wipe out your Windows 7 partition, though, would be to boot from Windows 10 USB flash drive and go through Windows 10 setup, after you select the custom install option, on the next screen pick the Windows 7 partition to install to. That will establish dual booting between two Windows 10 installs, but it should leave your original Windows 10 partition as the active system partition, then you can just remove the newly installed Windows 10 from the dual boot menu and reformat that same partition that used to be Windows 7.

Thank you @Brink, @NavyLCDR.
Managed to achieve what I was looking for. I Will post in short, what worked.
1.The bootable media repair option failed. The startup repair option returned with the error"Automatic repair couldn't repair your pc."
2.I booted with rescue win pe and using Minitools made the win7 partition Active again. This booted my PC normally in Win10 again.Once in Win 10 again followed all the steps " diskpart-select vol c- active- exit then, bcdboot C:\Windows /s C: /f BIOS -exit" . That too gave me same NTLDR missing error again.
3.Booted again with rescue PE and used Macrium Reflect to repair. Selected the Win10 partition to repair and rebooted. This time PC booted properly but Win7 option appeared again in OS selection menu.(previously removed in MSCONFIG).After booting deleted the Win7 entry again using MSCONFIG.Checked in Disk Management and found Win10 partion Active.
4.Formatted Win7 partition successfully from windows explorer context menu. This partition was on the left side in disk management and couldnt merge with the other data partition.So booted in rescue PE again and using AOMEI Partition merged the two partitions successfully.(now showing on the right side in disk management )

Thanks guys once again.

Glad you got it all sorted out!