We've all been there - someone runs wild with icacls or the security tab, and suddenly entire directory trees become inaccessible. When you're facing incorrectly set NTFS permissions that prevent access to user data, you need a surgical approach to reset permissions without destroying the file structure.

For this operation, we'll need:

1. Administrative Command Prompt
2. icacls.exe (built into Windows)
3. takeown.exe (for ownership issues)
4. A healthy dose of patience

First, we need to reclaim ownership of the entire drive:

takeown /f D:\ /r /d y

Then reset permissions recursively using icacls:

icacls D:\ /reset /t /c /q

For particularly stubborn permission issues, this nuclear option might be necessary:

icacls D:\ /grant Everyone:(OI)(CI)F /t /c /q

When dealing with user profiles, you might encounter permission issues with AppData. Here's a targeted fix:

icacls "D:\Users\*" /reset /t /c /q
icacls "D:\Users\*\AppData" /grant "%USERNAME%":(OI)(CI)F /t

For frequent use cases, create a batch script:

@echo off
setlocal
set DRIVE=D:
echo Resetting permissions on %DRIVE%...
takeown /f %DRIVE%\ /r /d y >nul
icacls %DRIVE%\ /reset /t /c /q >nul
echo Permission reset complete
endlocal

Remember that resetting permissions:

• Will break any custom permission schemes
• Should be done before OS reinstallation
• May require additional steps for system folders

When NTFS permissions get corrupted or misconfigured across an entire drive, it can prevent access to critical user data - especially when preparing for OS reinstallation. Here's how to systematically reset permissions while preserving data integrity.

Before modifying permissions:

# Take ownership first (Administrator CMD)
takeown /f D: /r /d y
icacls D: /reset /t /c /l

For Windows 8/Server 2012 or later:

$drive = "D:"
$acl = Get-Acl $drive
$defaultInheritance = $acl.SetAccessRuleProtection($false, $true)
Set-Acl -Path $drive -AclObject $acl

Get-ChildItem $drive -Recurse | ForEach-Object {
    try {
        $_.SetAccessControl($acl)
    }
    catch {
        Write-Warning "Failed on $($_.FullName): $_"
    }
}

For complete permission reset (use cautiously):

icacls D:\\* /reset /T /C /Q
icacls D:\\ /reset /T /C /Q

To preserve user profile permissions while resetting others:

# Reset entire drive except Users folder
icacls D:\\* /reset /T /C /Q /EXCLUDE "Users\\*"

# Then apply proper user permissions
icacls "D:\\Users\\*" /grant:r "CREATOR OWNER:(OI)(CI)(IO)F"

After resetting permissions:

# Check effective permissions
icacls D:\\ /verify /T

# Reapply standard inherited permissions
icacls D:\\ /inheritance:e /T