0x80070020

What it means

The installer tried to replace a file that something else had open. Microsoft attributes this to non-Microsoft filter drivers, most often antivirus, and to backup or scanning tools holding the file at the wrong moment.

Real causes

• Antivirus or antimalware is scanning the file the update needs to replace.
• A backup agent has the file open.
• Another install is touching the same files.

What to do

1. Perform a clean restart and retry the installation.
2. To identify the holder, run Process Monitor, reproduce the failure, then find the failing file in CBS.log and filter Procmon on that path.
3. Once you know which process holds the file, stop or exclude it and retry.
4. In a managed fleet, an antivirus exclusion for the servicing paths is the durable fix rather than per-device work.

Where to look

• %windir%\Logs\CBS\CBS.log

Checked against Microsoft documentation. Last reviewed 2026-08-20.

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