Service already running? Here's the real fix for 0X00000420

The 30-second fix: Stop it properly

This error shows up when you try to start a service that's already running—but you can't see it in Services.msc. Happened to me last month with a client's SQL Server agent on Windows Server 2019. The service looked stopped, but starting it gave 0X00000420.

Here's what you do first:

1. Open Services.msc (press Win+R, type services.msc, hit Enter).
2. Find the service that's giving you the error. Right-click it and choose Stop.
3. Wait 5 seconds. Then right-click again and choose Start.

That works maybe 40% of the time. If the service won't stop, move to the next step. Don't waste time rebooting—that's overkill for this.

The 5-minute fix: Kill it from the command line

When Services.msc won't stop it, the service is hanging on to a process that didn't close properly. I see this a lot with third-party services—like backup agents or VPN clients—that don't clean up after themselves.

Open an elevated Command Prompt (right-click Command Prompt, Run as Administrator). Then run:

sc query | find "SERVICE_NAME"

This lists all service names. Find yours—it'll be something like MyService or MyService_Svc. Then stop it with:

sc stop MyService

If that returns "The service has not been started" but you still get 0X00000420 when starting it, the service might be running under a different display name or a duplicate instance. Check with:

tasklist /svc | find "MyService"

That shows if the process is running with service host (svchost.exe). If you see a PID (process ID), kill it directly:

taskkill /F /PID 1234

Replace 1234 with the actual PID. Then try starting the service again from Services.msc.

The 15-minute fix: Find and remove the duplicate service

Sometimes there's a real duplicate—two service entries pointing to the same executable. I had a client whose print spooler had this issue after they installed a third-party print driver. Two spooler instances, but only one showed in Services.msc.

Open Registry Editor (regedit) as Administrator. Go to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services

Find your service name in the list. Expand it. Look for a DependencyOnService or ImagePath value that points to a different service. If you see something like MyService_Old or MyService_1, that's the duplicate.

Before deleting anything, export the key as a backup (right-click, Export). Then delete the duplicate key. Reboot the server. Start the service.

If that doesn't work, check Event Viewer under Windows Logs > System for warnings about "duplicate service" or "service control manager." Sometimes the event log tells you the exact service name causing the conflict.

One more thing: Check for orphaned processes

Had a case where a service kept crashing and the automatic restart created a zombie process. Use PowerShell to find all instances:

Get-CimInstance Win32_Service | Where-Object {$_.Name -like "*MyService*"}

If you see multiple entries with different ProcessId values, kill them all with Stop-Process -Id X -Force. Then start the service fresh.

That's it. No need to rebuild the server or reinstall the software. Just stop the hidden instance.