This article is intended for advanced computer users. If you are not comfortable with advanced troubleshooting, you might want to ask someone for help or contact support. For information about how to do this, visit the following Microsoft Web site:

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The problem may occur because of one or more of the following circumstances:

•	You may be experiencing a Windows Update issue.
•	The SoftwareDistribution folder may be corrupted.

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To resolve this problem, log on to the user account by using administrative credentials, and then use one of the following methods.

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Method 1: Manually install the Windows Defender Update Definitions

Microsoft delivers Windows Defender updates by using Windows Update. In some cases, you may receive errors because of problems from one of these services that are not related to Windows Defender itself. The first step is to try to manually install the update definitions. To manually install the update definitions, follow these steps:

1.	Visit the Security Portal. To do this, visit the following Microsoft Web site: http://www.microsoft.com/security/portal/ADL.aspx#top (http://www.microsoft.com/security/portal/ADL.aspx#top)
2.	Follow the appropriate steps.
3.	If you still receive "Windows Defender Definitions haven't been updated" warning messages, you might want to ask someone for help or contact support. For information about how to do this, visit the following Microsoft Web site: http://go.microsoft.com/fwlink/?linkID=21608 (http://go.microsoft.com/fwlink/?linkID=21608)

Note The following methods contain advanced troubleshooting steps. If you are not comfortable with advanced troubleshooting, you might want to ask someone for help. No charge support is available for consumers by calling 1-866-PCSAFETY in the United States and in Canada or by contacting your local Microsoft subsidiary. For more information about how to contact your local Microsoft subsidiary for update support issues, visit the following Microsoft International Support Web site: Enterprise customers can obtain support for updates through their usual support contacts.

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Method 2: Rename the SoftwareDistribution folder

1.	Exit all open programs.
2.	Click Start, click Run, type cmd, and then click OK.
3.	At the command prompt, type the following command to rename the SoftwareDistribution folder: net stop wuauserv net stop bits ren %systemroot%\SoftwareDistribution SoftwareDistribution.old net start wuauserv net start bits

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Method 3: Verify that you are not experiencing Microsoft Windows Update, Automatic Updates, and Windows Server Update Service (WSUS) problems

Microsoft delivers Defender Updates by using Microsoft Windows Update, Automatic Updates, and Windows Server Update Services (WSUS). In some cases, you may receive errors caused by problems from one of these services that are not related to Defender itself. To troubleshoot a potential Windows Update problem, follow these steps.

Windows Vista

1.

Examine the Windowsupdate.log file for error messages. To view the log file, follow these steps: a. Click Start. b. In the Start Search dialog box, type %\windowsupdate.log, and then press ENTER. For more information about how to read the Windowsupdate.log file, click the following article number to view the article in the Microsoft Knowledge Base: 902093 (http://support.microsoft.com/kb/902093/) How to read the Windowsupdate.log file

2.

Visit the Windows Help and How-to Web site, and then type the keywords that describe the problem: http://windowshelp.microsoft.com/windows/en-us/search.aspx?=&qu=%22windows+update+error%22 (http://v5.windowsupdate.microsoft.com/windowsupdate/v6/troubleshoot.aspx)

Windows 2000, Windows XP, and Windows Server 2003

1.	Examine the Windowsupdate.log file for error messages. To view the log file, click Start, click Run, type %windir%\windowsupdate.log in the Open box, and then press ENTER. For more information about how to read the Windowsupdate.log file, click the following article number to view the article in the Microsoft Knowledge Base: 902093 (http://support.microsoft.com/kb/902093/) How to read the Windowsupdate.log file a.
2.	Visit the following Microsoft Web site: http://v5.windowsupdate.microsoft.com/windowsupdate/v6/troubleshoot.aspx (http://v5.windowsupdate.microsoft.com/windowsupdate/v6/troubleshoot.aspx)
3.	On the Options Web page, type keywords that describe the problem.

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If you are still experiencing problems, you may be experiencing a different problem. You may find the following articles helpful. If these articles do not help you resolve the problem or if you experience symptoms that differ from those that are described in this article, search the Microsoft Knowledge Base for more information. To search the Microsoft Knowledge Base, visit the following Microsoft Web site: Then, type the text of the error message that you receive, or type a description of the problem in the Search Support (KB) field.

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