Windows Event ID 21 – System: Device Driver Installation Error

Start by examining the complete event details to identify the specific driver causing the failure.

1. Open Event Viewer → Windows Logs → System
2. Filter for Event ID 21 using the filter option
3. Double-click the most recent Event ID 21 entry
4. Note the driver name, device instance ID, and error code in the description
5. Use PowerShell to gather additional driver information:

Get-WinEvent -FilterHashtable @{LogName='System'; Id=21} -MaxEvents 5 | Format-List TimeCreated, Id, LevelDisplayName, Message

# Get detailed driver information
Get-WindowsDriver -Online | Where-Object {$_.Driver -like "*problematic_driver_name*"}

# Check driver store for issues
pnputil /enum-drivers | findstr "problematic_driver_name"

Document the driver name and associated hardware for the next troubleshooting steps.

Replace the failing driver with an updated version or perform a clean reinstallation.

1. Open Device Manager (devmgmt.msc)
2. Locate devices with warning or error icons
3. Right-click the problematic device → Update driver
4. If automatic update fails, download the latest driver from the manufacturer
5. For manual installation, use PowerShell:

# Remove the problematic driver
pnputil /delete-driver oem##.inf /uninstall /force

# Install new driver
pnputil /add-driver C:\path\to\new_driver.inf /install

# Verify installation
Get-PnpDevice | Where-Object {$_.Status -eq "Error"}

6. Restart the system and verify Event ID 21 no longer appears
7. Check device functionality to ensure proper operation

If the driver is unsigned but known to be safe, temporarily disable signature enforcement for testing.

1. Open an elevated Command Prompt
2. Disable signature enforcement:

bcdedit /set testsigning on
bcdedit /set nointegritychecks on

3. Restart the system
4. Install the driver through Device Manager or PowerShell
5. Verify the driver loads without Event ID 21
6. Re-enable signature enforcement for security:

bcdedit /set testsigning off
bcdedit /set nointegritychecks off

For Windows 11 systems with Secure Boot, you may need to disable Secure Boot temporarily in UEFI settings. Always re-enable security features after driver installation.

Corrupted system files can cause driver loading failures. Perform comprehensive system integrity checks.

1. Run System File Checker in an elevated Command Prompt:

sfc /scannow

2. If SFC finds issues, run DISM to repair the Windows image:

DISM /Online /Cleanup-Image /CheckHealth
DISM /Online /Cleanup-Image /ScanHealth
DISM /Online /Cleanup-Image /RestoreHealth

3. Check driver store integrity:

# Verify driver store
pnputil /enum-drivers | findstr "ERROR"

# Check for driver conflicts
Get-WindowsDriver -Online | Where-Object {$_.BootCritical -eq $true} | Format-Table Driver, Version, Date

4. Rebuild driver database if corruption is detected:

pnputil /export-pnpstate pnpstate.pnp
pnputil /delete-driver * /uninstall /force
pnputil /add-driver C:\Windows\System32\DriverStore\FileRepository\*.inf /subdirs /install

Restart the system after repairs and monitor for Event ID 21 recurrence.

Perform deep analysis of driver registry entries and resolve complex conflicts.

1. Export current driver configuration for backup:

reg export HKLM\SYSTEM\CurrentControlSet\Services driver_backup.reg
reg export HKLM\SYSTEM\CurrentControlSet\Enum enum_backup.reg

2. Analyze driver registry entries:

# Check for orphaned driver entries
Get-ChildItem "HKLM:\SYSTEM\CurrentControlSet\Services" | Where-Object {$_.GetValue("ImagePath") -like "*problematic_driver*"}

# Identify driver dependencies
$driverKey = "HKLM:\SYSTEM\CurrentControlSet\Services\DriverName"
Get-ItemProperty $driverKey -Name "DependOnService" -ErrorAction SilentlyContinue

3. Check for hardware resource conflicts:

# View resource allocation
Get-WmiObject -Class Win32_SystemDriver | Where-Object {$_.State -eq "Stopped"} | Format-Table Name, State, Status

# Check device conflicts
Get-WmiObject -Class Win32_PnPEntity | Where-Object {$_.Status -ne "OK"} | Format-Table Name, Status, DeviceID

4. Clean orphaned registry entries:

reg delete "HKLM\SYSTEM\CurrentControlSet\Services\ProblematicDriver" /f
reg delete "HKLM\SYSTEM\CurrentControlSet\Enum\ROOT\LEGACY_PROBLEMATICDRIVER" /f

5. Force hardware re-enumeration:

# Trigger device re-enumeration
$devcon = "C:\Windows\System32\devcon.exe"
& $devcon rescan
& $devcon restart *