diff --git a/scripts/build-installer-win.ps1 b/scripts/build-installer-win.ps1
index 7dd678f..e7a3455 100644
--- a/scripts/build-installer-win.ps1
+++ b/scripts/build-installer-win.ps1
@@ -2,6 +2,7 @@ param(
     [string]$Version = "",
     [string]$BuildDir = "build\win",
     [string]$StagingDir = "dist\win",
+    [string]$WintunVersion = "0.14.1",
     [switch]$Sign,
     [string]$SignCert = ""
 )
@@ -59,7 +60,7 @@ try {
     
     # CMake configure
     Write-Info "Running CMake configure..."
-    cmake -B $BuildDir -DCMAKE_BUILD_TYPE=Release
+    cmake -B $BuildDir -A x64 -DCMAKE_BUILD_TYPE=Release
     if ($LASTEXITCODE -ne 0) {
         throw "CMake configure failed"
     }
@@ -98,13 +99,13 @@ try {
     
     # Download wintun.dll
     Write-Info "Downloading Wintun..."
-    $wintunUrl = "https://www.wintun.net/builds/wintun-0.14.1.zip"
+    $wintunUrl = "https://www.wintun.net/builds/wintun-$WintunVersion.zip"
     $tempDir = Join-Path $env:TEMP "wintun_build"
     if (-not (Test-Path $tempDir)) {
         New-Item -ItemType Directory -Path $tempDir -Force | Out-Null
     }
     
-    $wintunZip = Join-Path $tempDir "wintun-0.14.1.zip"
+    $wintunZip = Join-Path $tempDir "wintun-$WintunVersion.zip"
     
     try {
         Write-Info "Downloading from $wintunUrl..."
@@ -118,6 +119,13 @@ try {
             throw "wintun.dll not found in extracted archive"
         }
         
+        # Verify wintun.dll size sanity check (x64 is ~50-80 KB)
+        $actualSize = (Get-Item $wintunDll).Length
+        if ($actualSize -lt 30000 -or $actualSize -gt 200000) {
+            throw "wintun.dll size check failed ($actualSize bytes) — download may be corrupt or tampered"
+        }
+        Write-Info "wintun.dll verified ($actualSize bytes)"
+        
         Copy-Item -Path $wintunDll -Destination $StagingDir -Force
         Write-Success "Wintun.dll extracted and copied to $StagingDir"
     } finally {