Fix 0X0000050A: Service SID Type Error

You're staring at Event Viewer and there it is: ERROR_INCOMPATIBLE_SERVICE_SID_TYPE (0X0000050A). The service just won't start, and the error message doesn't tell you much. I've seen this on Windows Server 2019 and Windows 10/11 boxes, often right after a service is installed or an update rolls out. It happens with third-party services that try to run as LocalSystem but haven't been set up to handle the newer SID type enforcement.

The root cause is simple once you know it. Every service on Windows has a security identifier (SID). Since Vista, Windows can assign SIDs to services to isolate them. The registry holds a value called ServiceSidType that controls this. When the value is missing or set to something the OS doesn't like, you get this error. The service's executable might be fine — it's just the registry entry that's off.

You can fix this in a few minutes with a registry edit and a restart of the service. I'll walk you through it, and I'll tell you exactly what to expect at each step.

Before you start

You'll need administrator rights on the machine. If this is a domain server, make sure you're logged in as a domain admin or have been given local admin rights.

Fix the registry

Press Win + R, type regedit, and hit Enter. Click Yes when UAC pops up.
Go to this key:
```
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<YourServiceName>
```
Replace <YourServiceName> with the actual service name. You can find it in Services (services.msc) under the 'Service name' column, not the display name.
Look on the right side for a value called ServiceSidType. If it exists, double-click it. If it doesn't, right-click on empty space and choose New > DWORD (32-bit) Value, then name it ServiceSidType.
Set the value to 1. That tells Windows to use the service's SID in restricted mode, which is usually the fix. Click OK.
Close regedit.
Restart the service. Open an admin Command Prompt and run:
```
sc stop <YourServiceName>
```
Then:
```
sc start <YourServiceName>
```

After you run sc start, you should see a message like "SERVICE_NAME: YourService" and the status should go to RUNNING. If it fails again, you'll see the error code again.

If the service still won't start

Sometimes the issue is that the service is set to run under a different account, like a domain user, and that account needs the SID type to be 2 (unrestricted) instead. Try setting ServiceSidType to 2 and restart the service.

Another thing to check: the service's executable path. Right-click the service in services.msc, go to Properties, and look at the 'Path to executable'. Make sure it points to a real file that exists. A missing binary will sometimes throw this exact error, even though the SID type is correct.

If you've set it to 1, then 2, and the path is fine, look at the service's dependencies. Some services need others to be running first. Check the 'Dependencies' tab in the service properties. If a dependency isn't started, you'll get a different error usually, but I've seen cases where it masked as this one.

One more thing: check if the service has a RequiredPrivileges value in the same registry key. If that list is missing a privilege the service needs, the OS might reject it with this error. I've only seen this on custom services, not off-the-shelf software, but it's worth a look if you're stuck.

After you make any registry change, remember to restart the service. Don't restart the whole server yet — that's overkill unless you've changed multiple services. You can also use the Services console to restart it: right-click and choose 'Restart'.

In my experience, setting ServiceSidType to 1 fixes 9 out of 10 cases. If you're still getting the error after trying both values and checking paths, I'd look at the service's install logs or contact the vendor. But I'm betting the registry edit does it for you.