diff --git a/RunCommand/Windows/Windows_OSUpgrade_Assessment_Validation/Windows_OSUpgrade_Assessment_Validation.ps1 b/RunCommand/Windows/Windows_OSUpgrade_Assessment_Validation/Windows_OSUpgrade_Assessment_Validation.ps1
index 00618c3..570c5a7 100644
--- a/RunCommand/Windows/Windows_OSUpgrade_Assessment_Validation/Windows_OSUpgrade_Assessment_Validation.ps1
+++ b/RunCommand/Windows/Windows_OSUpgrade_Assessment_Validation/Windows_OSUpgrade_Assessment_Validation.ps1
@@ -33,6 +33,30 @@ Disclaimer:
     PS> .\Windows_OSUpgrade_Assessment_Validation.ps1
 #>
 
+# ---- Legacy driver and GlobalFlag detection ----------------------------------
+function Get-LegacyDriverBlockers {
+    # Known legacy VMware / ghost hardware drivers that cause 0xC1900101-0x50016
+    $knownBlockers = @('vmmouse', 'vm3dmp', 'flpydisk', 'vmhgfs', 'vmrawdsk', 'vmusbmouse', 'vmvss', 'vmscsi', 'vmxnet')
+    $found = @()
+    foreach ($name in $knownBlockers) {
+        $svcPath = "HKLM:\SYSTEM\CurrentControlSet\Services\$name"
+        if (Test-Path $svcPath) {
+            $start = (Get-ItemProperty $svcPath -ErrorAction SilentlyContinue).Start
+            # Start values: 0=Boot, 1=System, 2=Auto, 3=Manual, 4=Disabled
+            if ($null -ne $start -and $start -le 3) {
+                $found += $name
+            }
+        }
+    }
+    return $found
+}
+
+function Get-GlobalFlagStatus {
+    $smPath = "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager"
+    $gf = (Get-ItemProperty $smPath -Name GlobalFlag -ErrorAction SilentlyContinue).GlobalFlag
+    return ($null -ne $gf -and $gf -ne 0)
+}
+
 # ---- Safety checks -----------------------------------------------------------
 function Assert-Admin {
     $isAdmin = ([Security.Principal.WindowsPrincipal] `
@@ -202,6 +226,10 @@ if ($isServer) {
     }
 }
 
+# --- Run legacy driver and GlobalFlag checks (server IPU blocker detection) ---
+$legacyDriverBlockers = Get-LegacyDriverBlockers
+$globalFlagEnabled    = Get-GlobalFlagStatus
+
 # --- Checklist Output ---
 $checklist = @()
 $checklist += "Windows Version: $windowsProductName"
@@ -256,6 +284,30 @@ if ($isServer) {
     }
 }
 
+# Legacy Driver / Ghost Hardware Check (IPU blocker)
+if ($legacyDriverBlockers.Count -gt 0) {
+    $checklist += "[Failed] Legacy IPU-blocking drivers detected: $($legacyDriverBlockers -join ', ')"
+    $messages += ""
+    $messages += "FAILED: Legacy VMware/ghost hardware drivers are present and set to load. These will cause IPU to fail with error 0xC1900101-0x50016 (SafeOS boot crash)."
+    $messages += "  Drivers found: $($legacyDriverBlockers -join ', ')"
+    $messages += "  Action: In Device Manager, DISABLE (do not uninstall) each legacy device before retrying IPU."
+    $messages += "  Note: Uninstalling may allow PnP to reinstall the driver on next reboot. Disable ensures it stays dormant during upgrade."
+} else {
+    $checklist += "[Passed] No legacy IPU-blocking drivers detected"
+}
+
+# GlobalFlag (PageHeap/debug mode) Check
+if ($globalFlagEnabled) {
+    $checklist += "[Failed] GlobalFlag debug mode is enabled (causes throttled Setup and slow IPU rollback)"
+    $messages += ""
+    $messages += "FAILED: GlobalFlag is enabled in Session Manager. This forces Windows Setup to run in debug/PageHeap mode, causing severely throttled memory operations during IPU and a guaranteed rollback."
+    $messages += "  Action: Disable GlobalFlag before retrying IPU:"
+    $messages += '  reg delete "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager" /v GlobalFlag /f'
+    $messages += "  Then reboot the VM before attempting the in-place upgrade."
+} else {
+    $checklist += "[Passed] GlobalFlag debug mode is not enabled"
+}
+
 # Output checklist first, then messages
 $checklist | ForEach-Object { Write-Output $_ }
 $messages | ForEach-Object { Write-Output $_ }