When attempting to enforce Medium security level for the Internet zone through Group Policy in a mixed Server 2003 (DC) and Server 2008 (client) environment, administrators often encounter unexpected behavior where settings appear applied in GPResult but don't reflect in Internet Explorer.

Internet Explorer security zones are controlled through registry keys under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones. The Internet zone (zone 3) requires proper value setting for security levels:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3]
"CurrentLevel"=dword:00011000
"MinLevel"=dword:00011000
"RecommendedLevel"=dword:00011000

To properly diagnose the issue, follow this verification sequence:

1. Run gpupdate /force on client
2. Execute rsop.msc to verify policy application
3. Check registry values with this PowerShell command:

   Get-ItemProperty -Path "HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3" | 
   Select-Object CurrentLevel,MinLevel,RecommendedLevel
   

For Server 2003 DC managing Server 2008 clients, consider these alternatives:

• Create a custom ADM template with explicit registry values
• Use Group Policy Preferences to directly modify registry
• Implement a logon script with registry modification commands

For environments where GPO isn't effective, this PowerShell script can enforce settings:

# Set Internet Zone to Medium security
$regPath = "HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3"
$mediumValue = 0x00011000

if (-not (Test-Path $regPath)) {
    New-Item -Path $regPath -Force | Out-Null
}

Set-ItemProperty -Path $regPath -Name "CurrentLevel" -Value $mediumValue -Type DWord
Set-ItemProperty -Path $regPath -Name "MinLevel" -Value $mediumValue -Type DWord
Set-ItemProperty -Path $regPath -Name "RecommendedLevel" -Value $mediumValue -Type DWord

# Refresh Internet Explorer settings
$signature = @'
[DllImport("wininet.dll", SetLastError = true)]
public static extern bool InternetSetOption(IntPtr hInternet, int dwOption, IntPtr lpBuffer, int dwBufferLength);
'@
$internetSetOption = Add-Type -MemberDefinition $signature -Name "Win32InternetSetOption" -Namespace Win32Functions -PassThru
$internetSetOption::InternetSetOption([IntPtr]::Zero, 39, [IntPtr]::Zero, 0) | Out-Null

After implementation, verify with these techniques:

• Clear IE cache and restart the browser
• Check Event Viewer for policy application errors
• Compare client-side registry with DC policy definitions
• Use Process Monitor to trace registry access during policy application

When configuring Internet Explorer security zones through Group Policy in mixed Server 2003/2008 environments, administrators often encounter situations where policies appear to apply correctly in GPResult but don't reflect in actual browser settings. The core challenge lies in the policy processing hierarchy and version-specific registry handling.

First, verify if the policy is actually writing to the registry. Check this key on the target machine:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3]
"CurrentLevel"=dword:00011000
"MinLevel"=dword:00011000
"RecommendedLevel"=dword:00011000

The value 00011000 corresponds to Medium security level. If these values are missing or incorrect, we need to force policy processing.

Create a batch script to refresh policies and reset IE settings:

@echo off
:: Force group policy update
gpupdate /force

:: Reset IE zone settings
reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones" /f
reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Lockdown_Zones" /f

:: Restart IE processes
taskkill /f /im iexplore.exe
start "" "C:\Program Files\Internet Explorer\iexplore.exe"

For Server 2003 DCs, ensure you're using the correct ADM templates. The Internet Explorer security settings require inetres.adm to be loaded in your GPO. Verify this through:

Get-ChildItem "C:\Windows\inf\" -Filter *.adm | Where-Object {$_.Name -like "*inetres*"}

For mixed environments, implement this PowerShell script that accounts for OS version differences:

# Detect OS version and apply appropriate zone settings
$osVersion = [Environment]::OSVersion.Version
$zonePath = "HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3"

if ($osVersion.Major -eq 6 -and $osVersion.Minor -eq 0) {
    # Server 2008 specific handling
    Set-ItemProperty -Path $zonePath -Name "CurrentLevel" -Value 0x00011000 -Type DWord
    Set-ItemProperty -Path $zonePath -Name "Flags" -Value 0x00000003 -Type DWord
} else {
    # Default handling for other versions
    Set-ItemProperty -Path $zonePath -Name "CurrentLevel" -Value 0x00011000 -Type DWord
}

# Force IE to recognize changes
$signature = @'
[DllImport("wininet.dll", SetLastError = true)]
public static extern bool InternetSetOption(IntPtr hInternet, int dwOption, IntPtr lpBuffer, int dwBufferLength);
'@
$interopHelper = Add-Type -MemberDefinition $signature -Name "WinINet" -Namespace "Interop" -PassThru
$interopHelper::InternetSetOption([IntPtr]::Zero, 39, [IntPtr]::Zero, 0) | Out-Null

After implementation:

1. Run gpresult /h gpresult.html and verify policy application
2. Check registry values match expected settings
3. Test with multiple user profiles
4. Monitor Event Viewer for policy-related errors