RPC_S_ENTRY_ALREADY_EXISTS (0x000006E0) – Quick Fix

You're Stuck, Let's Fix It

I know the drill—you're trying to get something running, and Windows throws this cryptic RPC_S_ENTRY_ALREADY_EXISTS (0x000006E0) error. It's not a crash, it's not a bluescreen, it's an annoying roadblock. Let's get past it.

The Fix: Clear the Duplicate RPC Entry

This error means the RPC endpoint mapper already has an entry for whatever you're trying to register. That happens when a previous install or configuration didn't clean up after itself. Here's how to fix it:

Step 1: Find the Offending Entry

Open Command Prompt as Administrator. Run:

rpcdump | findstr /i "0x000006E0"

That'll show you which interface or endpoint is duplicated. If rpcdump isn't installed (it's part of the Windows SDK), use PowerShell instead:

Get-WmiObject -Class Win32_DCOMApplication

Look for entries with duplicate AppIDs or names. Had a client last month whose print queue died because of a duplicate RPC entry from a failed printer driver update. Same error.

Step 2: Remove the Duplicate

Once you know the interface UUID or AppID, run this to unregister it:

rpcremove /uuid:{your-uuid-here}

If rpcremove isn't available (it's not on all systems), use the Registry Editor. Navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Rpc\

Look under the NameService or EndpointMapper keys. Delete the duplicate entry. Be careful—don't delete the whole key, just the duplicate.

Step 3: Restart the RPC Service

After removing the duplicate, restart the RPC service:

net stop RpcSs && net start RpcSs

Or just reboot the server—it's faster and safer. I always reboot after registry edits.

Why This Works

The RPC endpoint mapper is like a phone book for services. When a program registers itself, it adds an entry. If that entry already exists (from a previous registration that didn't unregister properly), Windows refuses to add it again. That's what 0x000006E0 means: "the entry already exists."

Cleaning out the duplicate lets the new registration happen cleanly. This is common after upgrading software that uses DCOM (like SQL Server or Exchange) without properly uninstalling the old version first.

Less Common Variations

1. The Entry Is in a Different Store

Sometimes the duplicate isn't in the main RPC registry hive. Check these locations too:

• HKEY_CLASSES_ROOT\AppID\{your-appid}
• HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AppID\{your-appid}

Delete any duplicate AppID entries there. Then restart the RPC service.

2. The Error Comes From a Specific Application

Some apps manage their own RPC entries. If the error happens when starting a specific program (like a backup agent or monitoring tool), check that app's configuration files. Look for a .ini or .cfg file with a duplicate endpoint definition. Delete or rename it, then restart the app.

Had a client whose backup software kept failing after a server migration. The old server's endpoint was still in the config file. Deleted that line, and it worked immediately.

3. Network-Related Duplicate Entries

On domain controllers, this error can happen when the NTDS or Netlogon services register duplicate RPC entries. That's rare, but if you're on a domain controller, check Event ID 1925 or 1926. The fix is to demote and re-promote the DC—or just restore from a known good backup.

Prevention

Stop this from happening again with two simple rules:

• Always uninstall properly. Don't just delete program folders—use the official uninstaller. That triggers the proper RPC unregistration.
• Use a consistent naming convention. If you're registering custom RPC interfaces, keep a log of UUIDs and app names. A spreadsheet works. That way you'll spot duplicates before they cause errors.

And if you're migrating services between servers, export the RPC registry keys from the old server first—you can import them cleanly on the new one without duplicates.