diff --git a/windows/branding/lib/RegistryHelpers.ps1 b/windows/branding/lib/RegistryHelpers.ps1
new file mode 100644
index 0000000..943aed8
--- /dev/null
+++ b/windows/branding/lib/RegistryHelpers.ps1
@@ -0,0 +1,16 @@
+Set-StrictMode -Version Latest
+
+# Write a registry value under an arbitrary hive root (a live HKLM:/HKCU: path
+# OR a loaded offline hive exposed as a PSDrive). Creates intermediate keys.
+function Set-SmRegValue {
+    param(
+        [Parameter(Mandatory)][string]$Root,
+        [Parameter(Mandatory)][string]$SubKey,
+        [Parameter(Mandatory)][string]$Name,
+        [Parameter(Mandatory)][ValidateSet('String','ExpandString','DWord','Binary')][string]$Type,
+        [Parameter(Mandatory)]$Value
+    )
+    $key = Join-Path $Root $SubKey
+    if (-not (Test-Path $key)) { New-Item -Path $key -Force | Out-Null }
+    New-ItemProperty -Path $key -Name $Name -PropertyType $Type -Value $Value -Force | Out-Null
+}
diff --git a/windows/tests/Branding.Tests.ps1 b/windows/tests/Branding.Tests.ps1
new file mode 100644
index 0000000..f7cb680
--- /dev/null
+++ b/windows/tests/Branding.Tests.ps1
@@ -0,0 +1,22 @@
+#Requires -Modules @{ ModuleName='Pester'; ModuleVersion='5.0.0' }
+
+Describe 'Set-SmRegValue' {
+    BeforeAll {
+        . "$PSScriptRoot\..\branding\lib\RegistryHelpers.ps1"
+        $script:root = 'HKCU:\Software\SilverMetalTest'
+        if (Test-Path $script:root) { Remove-Item $script:root -Recurse -Force }
+    }
+    AfterAll {
+        if (Test-Path $script:root) { Remove-Item $script:root -Recurse -Force }
+    }
+
+    It 'creates the key path and writes a string value' {
+        Set-SmRegValue -Root $script:root -SubKey 'A\B' -Name 'Greeting' -Type String -Value 'hi'
+        (Get-ItemProperty "$script:root\A\B").Greeting | Should -Be 'hi'
+    }
+
+    It 'writes a dword value' {
+        Set-SmRegValue -Root $script:root -SubKey 'A' -Name 'Flag' -Type DWord -Value 1
+        (Get-ItemProperty "$script:root\A").Flag | Should -Be 1
+    }
+}