How to create a registry hive file from a .reg backup

Question

Long story short, I accidentally royally screwed up my HKLM\SYSTEM registry directory trying to fix WinApps permissions that were changed with a Windows security patch.

As of right now, my system is completely unable to boot with a BSOD message of "inaccessible boot device" caused by my changes. I've tried

• changing values of registry keys to enable AHCI
• Safe Mode
• sfc /scannow + chkdsk
• Checking for pending packages in DISM
• Moving files from Regback to /config

• importing my working backup of SYSTEM.reg into the registry under windows recovery command prompt and WinPE

  One of those would normally work, but my issue is caused by a junk SYSTEM registry.

I need to create a SYSTEM HIVE file from my .REG backup of the HKLM\SYSTEM directory.

I thought this would be a very simple solution, but the only thing that I've managed to find on this topic is a random MSDN post from years ago that seems like it would accomplish what I want, but I can't get the script to work. (https://blogs.msdn.microsoft.com/sergey_babkins_blog/2014/11/10/how-to-create-a-brand-new-registry-hive/)

• Trying to run his script as a .bat returns an error stating:function' is not recognized as an internal or external command, operable program or batch file.
• Trying to run the .bat in powershell returns: merge.bat : The term 'merge.bat' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

If anyone knows how to get the above powershell script to work, please let me know.

Answer 1

The script you have linked is a PowerShell script, it needs to be saved with a .ps1 extension and executed in PowerShell.

Can you try saving it as a .ps1 file and running it, does this resolve your issues?

Edit:

The contents of your .ps1 file should be:

function ConvertTo-RegistryHive
{
<#
.SYNOPSIS
Convert a registry-exported  text (contents of a .reg file) to a binary registry hive file.

.EXAMPLE
PS> ConvertTo-RegistryHive -Text (Get-Content my.reg) -Hive my.hive
#>
    param(
        ## The contents of registry exported (.reg) file to convert into the hive.
        [string[]] $Text,
        ## The hive file name to write the result to.
        [parameter(Mandatory=$true)]
        [string] $Hive
    )

    $basefile = Join-Path ([System.IO.Path]::GetTempPath()) ([System.IO.Path]::GetRandomFileName())
    $regfile = $basefile + ".reg"
    $inifile = $basefile + ".ini"
    $subkey = [System.Guid]::NewGuid().ToString()

    &{
        foreach ($chunk in $Text) {
            foreach ($line in ($chunk -split "`r")) {
                $line -replace "^\[\w*\\\w*","[HKEY_LOCAL_MACHINE\$subkey"
            }
        }
    } | Set-Content $regfile

    # Since bcdedit stores its data in the same hives as registry,
    # this is the way to create an almost-empty hive file.
    bcdedit /createstore $Hive
    if (!$?) { throw "failed to create the new hive '$Hive'" }

    reg load "HKLM\$subkey" $Hive
    if (!$?) { throw "failed to load the hive '$Hive' as 'HKLM\$subkey'" }

    try {
        # bcdedit creates some default entries that need to be deleted,
        # but first the permissions on them need to be changed to allow deletion
@"
HKEY_LOCAL_MACHINE\$subkey\Description [1]
HKEY_LOCAL_MACHINE\$subkey\Objects [1]
"@ | Set-Content $inifile
        regini $inifile
        if (!$?) { throw "failed to change permissions on keys in 'HKLM\$subkey'" }
        Remove-Item -LiteralPath "hklm:\$subkey\Description" -Force -Recurse
        Remove-Item -LiteralPath "hklm:\$subkey\Objects" -Force -Recurse

        # now import the file contents
        reg import $regfile
        if (!$?) { throw "failed to import the data from '$regfile'" }
    } finally {
        reg unload "HKLM\$subkey"
        Remove-Item -LiteralPath $inifile -Force
    }

    Remove-Item -LiteralPath $regfile -Force
}

ConvertTo-RegistryHive -Text (Get-Content C:\MyHive.reg) -Hive HiveName

And then just change this C:\MyHive.reg to point to your .reg file and HiveName to the name of the Hive to be created.