вопрос: Я хочу программно (с PowerShell) стать владельцем файла, на который у меня нет абсолютно никаких разрешений.

Обновить: ЯМы тщательно переписали вопрос, чтобы предпринять шаги по его воспроизведению. Вот'что яя делаю:

##########################################################
# Logon as UserA
##########################################################

$file = "C:\temp\file.txt"
new-item C:\temp -type dir
new-item $file -type file

# Remove inheritence
$isProtected = $true
$preserveInheritance = $true
$FileSecurity = Get-ACL $file
$FileSecurity.SetAccessRuleProtection($isProtected, $preserveInheritance)
Set-ACL $file -AclObject $FileSecurity

# Remove authenticated users
$user = "Authenticated Users"
$permission = "Modify"
$Account = New-Object System.Security.Principal.NTAccount($user)
$FileSystemRights = [System.Security.AccessControl.FileSystemRights]$permission
$InheritanceFlag = [System.Security.AccessControl.InheritanceFlags]"ContainerInherit, ObjectInherit"
$PropagationFlag = [System.Security.AccessControl.PropagationFlags]"None"
$AccessControlType =[System.Security.AccessControl.AccessControlType]::Allow
$FileSystemAccessRule = New-Object System.Security.AccessControl.FileSystemAccessRule($Account, $FileSystemRights, $InheritanceFlag, $PropagationFlag, $AccessControlType)
$FileSecurity = Get-ACL $file
$FileSecurity.RemoveAccessRuleAll($FileSystemAccessRule)
Set-ACL $file -AclObject $FileSecurity

# Remove local users
$user = "BUILTIN\Users"
$permission = "ReadAndExecute"
$Account = New-Object System.Security.Principal.NTAccount($user)
$FileSystemRights = [System.Security.AccessControl.FileSystemRights]$permission
$InheritanceFlag = [System.Security.AccessControl.InheritanceFlags]"ContainerInherit, ObjectInherit"
$PropagationFlag = [System.Security.AccessControl.PropagationFlags]"None"
$AccessControlType =[System.Security.AccessControl.AccessControlType]::Allow
$FileSystemAccessRule = New-Object System.Security.AccessControl.FileSystemAccessRule($Account, $FileSystemRights, $InheritanceFlag, $PropagationFlag, $AccessControlType)
$FileSecurity = Get-ACL $file
$FileSecurity.RemoveAccessRuleAll($FileSystemAccessRule)
Set-ACL $file -AclObject $FileSecurity

# Give the current user Full Control
$user = $env:username
$permission = "FullControl"
$FileSystemRights = [System.Security.AccessControl.FileSystemRights]$permission
$AccessControlType =[System.Security.AccessControl.AccessControlType]::Allow
$Account = New-Object System.Security.Principal.NTAccount($user)
$FileSystemAccessRule = New-Object System.Security.AccessControl.FileSystemAccessRule($Account, $FileSystemRights, $AccessControlType)
$FileSecurity = Get-ACL $file
$FileSecurity.AddAccessRule($FileSystemAccessRule)
Set-ACL $file -AclObject $FileSecurity

# Remove local administrators
$user = "BUILTIN\Administrators"
$permission = "FullControl"
$Account = New-Object System.Security.Principal.NTAccount($user)
$FileSystemRights = [System.Security.AccessControl.FileSystemRights]$permission
$InheritanceFlag = [System.Security.AccessControl.InheritanceFlags]"ContainerInherit, ObjectInherit"
$PropagationFlag = [System.Security.AccessControl.PropagationFlags]"None"
$AccessControlType =[System.Security.AccessControl.AccessControlType]::Allow
$FileSystemAccessRule = New-Object System.Security.AccessControl.FileSystemAccessRule($Account, $FileSystemRights, $InheritanceFlag, $PropagationFlag, $AccessControlType)
$FileSecurity = Get-ACL $file
$FileSecurity.RemoveAccessRuleAll($FileSystemAccessRule)
Set-ACL $file -AclObject $FileSecurity

# Set the owner to be the current user
$user = $env:username
$Account = New-Object System.Security.Principal.NTAccount($user)
$FileSecurity = new-object System.Security.AccessControl.FileSecurity
$FileSecurity.SetOwner($Account)
[System.IO.File]::SetAccessControl($file, $FileSecurity)

##########################################################
# Log off the server as UserA and logon as UserB
##########################################################

$file = "C:\temp\file.txt"

# Take ownership
$user = $env:username
$Account = New-Object System.Security.Principal.NTAccount($user)
$FileSecurity = new-object System.Security.AccessControl.FileSecurity
$FileSecurity.SetOwner($Account)
[System.IO.File]::SetAccessControl($file, $FileSecurity)

Это выдает ошибку:

Exception calling "SetAccessControl" with "2" argument(s): "Attempted to perform an unauthorized operation."
At line:1 char:35
+ [System.IO.File]::SetAccessControl < ($path, $FileSecurity)
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : DotNetMethodException