Who This Affects and What to Do
This article is for small-business employees who see an alert or log entry referencing Event ID 43 on a Windows computer. This event is purely informational—it simply means Windows has started installing an update, such as a system patch, driver, Microsoft Store app, or Defender definition update. No action is required in most cases, and the event does not indicate an error or failure.
What Is Event ID 43?
Event ID 43 is recorded in the System log by the source Microsoft-Windows-WindowsUpdateClient whenever Windows begins an update installation. The log entry reads: Windows has started installing the following update: [App/Update Name]. It is classified as an informational event, not a warning or error.
Common scenarios that trigger this event include:
- A scheduled or user-initiated Windows update beginning to install.
- Microsoft Store apps or Defender definition updates starting in the background.
- A third-party app updating through the Microsoft Store or your organization’s update service.
When No Action Is Needed
If you see Event ID 43 and nothing seems wrong with your computer, you do not need to do anything. The update is simply in progress. This is normal, expected behavior.
When to Pay Closer Attention
You should take note—or contact your IT support team—if any of the following are true:
- The same update appears to be starting repeatedly without ever finishing successfully.
- Follow-up error events appear in the logs, particularly Event ID 45 or Event ID 20, which indicate an update failure.
- The update involves an app or software that is not approved for use at your organization.
- Your computer becomes slow, unstable, or behaves unusually after an update attempt.
- The device appears to be stuck in a loop of failed updates.
- An update appears to be blocked or restricted by a company policy.
Steps to Take If Issues Are Present
- Note exactly which update is named in the Event ID 43 log entry.
- Check whether a follow-up error—especially Event ID 45 or Event ID 20—appears in the same System log after the Event ID 43 entry.
- Record whether the same update name appears in multiple Event ID 43 entries without a corresponding successful completion.
- Note any unusual behavior on the device, such as slowness, crashes, or application errors that began around the time of the update.
- Contact your IT support team and share the event details, including the update name, the event IDs observed, and a description of any problems. You can reach Advanced Computer Solutions at https://acsapp.com/contact-us/.
Summary
Event ID 43 is a routine, informational log entry that Windows creates every time an update installation begins. On its own, it requires no action. Only investigate further if the update fails to complete, causes system problems, or conflicts with your organization’s software policies.
Common questions
Is Event ID 43 a sign that something went wrong with Windows Update?
No. Event ID 43 is an informational event that simply means Windows has started installing an update. It does not indicate an error or failure. If an installation does fail, a separate event—such as Event ID 45 or Event ID 20—will appear in the System log.
What should I do if I keep seeing Event ID 43 for the same update over and over?
Repeated Event ID 43 entries for the same update, with no successful completion in between, can indicate that the update is stuck in a loop. Check the System log for follow-up error events such as Event ID 45 or Event ID 20, and contact your IT support team if the problem continues.
Can Event ID 43 appear for apps other than Windows system updates?
Yes. This event is triggered whenever Windows begins installing any update through its update client, including Microsoft Store apps, Defender definition updates, driver updates, and third-party apps that update through the Microsoft Store or your organization’s update service.