Microsoft small business knowledge base

Article ID: 2635095 - Last Review: May 25, 2012 - Revision: 5.0


After you are prompted to upgrade Microsoft Security Essentials, the upgrade doesn't install and you receive error 0x80070645.


To resolve this issue, uninstall Microsoft Security Essentials, delete any remaining registry subkeys, and then manually install the latest version of Microsoft Security Essentials.

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Note: Before you uninstall Microsoft Security Essentials, make sure that Windows Firewall is turned on.
Antivirus software helps protect your computer from viruses. You must not download or open files from sources that you do not trust, visit websites that you do not trust, or open email attachments when your antivirus software is disabled. For more information about computer viruses, see the following article in the Microsoft Knowledge Base:129972: How to prevent and remove viruses and other malware

To do this, follow these steps.

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Note: You may find it easier to follow the steps if you print this article first.

Step 1: Use Add or Remove Programs to uninstall Microsoft Security Essentials
Step 2: Back up the registry
Step 3: Delete registry subkeys for Microsoft Security Essentials
Step 4: Reinstall Microsoft Security Essentials


For more information about Microsoft Security Essentials, see the Microsoft Security Essentials website.

For information about support for Microsoft Security Essentials, see the Help and Support for Microsoft Security Essentials website.
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