Many system administrators need to enforce automatic screen locking after periods of inactivity as a security measure. While Windows provides screen saver timeout settings through GPO, the direct screen lock functionality isn't as immediately obvious in the Group Policy Editor.

The most reliable method to achieve automatic screen locking is actually through the screen saver settings with a specific configuration:

1. Navigate to: 
Computer Configuration > Policies > Administrative Templates > Control Panel > Personalization

2. Enable these policies:
- Force specific screen saver: "scrnsave.scr"
- Screen saver timeout: [your desired minutes]
- Password protect the screen saver: Enabled

For more granular control where GPO isn't sufficient, you can push these registry settings:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Control Panel\Desktop]
"ScreenSaveActive"="1"
"ScreenSaverIsSecure"="1"
"ScreenSaveTimeOut"="300"  ; 5 minutes in seconds
"SCRNSAVE.EXE"="scrnsave.scr"

After deploying either method, test with these PowerShell commands:

# Check current screen saver settings
Get-ItemProperty "HKCU:\Control Panel\Desktop" | Select-Object ScreenSaveActive, ScreenSaverIsSecure, ScreenSaveTimeOut

# Force immediate lock to test (requires user session)
rundll32.exe user32.dll,LockWorkStation

• If policies don't apply, run gpupdate /force and restart
• Ensure the screen saver .scr file exists in System32
• Check for conflicting settings in both Computer and User configurations
• Verify Windows editions support these GPO settings

For kiosk mode or terminal servers, consider these additional measures:

# Task Scheduler command to lock after idle detection
schtasks /create /tn "Lock After Idle" /tr "rundll32.exe user32.dll,LockWorkStation" /sc onidle /i 10

Many administrators mistakenly assume that configuring screensaver timeout in GPO will automatically lock the workstation. While related, these are actually separate settings in Windows Group Policy. The screensaver setting only controls visual display behavior, not security locking.

To properly enforce screen locking after idle time, you need to configure these two policies together:

Computer Configuration > Policies > Administrative Templates > Control Panel > Personalization
- Enable "Force specific screen saver"
- Set "Screen saver timeout" to your desired idle period (e.g., 900 seconds = 15 minutes)

Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options
- Configure "Interactive logon: Machine inactivity limit" to match your screensaver timeout

After applying these policies, test them by:

1. Running gpupdate /force on a test machine
2. Waiting the specified idle period
3. Confirming the workstation requires credentials to unlock

For more granular control, consider these additional settings:

# PowerShell script to verify settings
Get-ItemProperty "HKLM:\SOFTWARE\Policies\Microsoft\Windows\Control Panel\Desktop" | 
Select-Object ScreenSaveActive, ScreenSaveTimeOut, ScreenSaverIsSecure

# Registry path for direct configuration
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Control Panel\Desktop

If policies aren't applying correctly:

• Check Event Viewer for Group Policy errors
• Verify the GPO is linked to the correct OU
• Ensure no conflicting local or user policies exist
• Check if the screensaver .scr file exists in System32

For maximum security:

• Set timeout to 15 minutes or less for high-security areas
• Combine with password-protected screensaver
• Enable "Require Ctrl+Alt+Del" for additional security
• Consider implementing Credential Guard for sensitive environments