After you install Microsoft Windows Defender in Microsoft Windows XP or in Microsoft Windows Server 2003, you may receive the following "Check for new definitions" warning:In addition, the Check for updates now button is unavailable.

If you check for updated definitions by clicking Check for Updates under the Windows Defender Help option, Windows Defender reports that no updates are available.

Note This problem may also occur in Windows Vista. Windows Defender is one of the features of Windows Vista.

Back to the top

This problem occurs because Windows Defender could not automatically update the definitions.

Back to the top

To resolve this problem, follow these steps:

1.

Open Windows Defender. To do this, click Start, click Programs, and then click Windows Defender.

2.

Check for new definitions. To do this, follow these steps: a. Click Start, click Programs, and then click Windows Defender. b. Click the Help options arrow next to the Windows Defender Help icon, and then click Check for Updates. Notice that the notification balloon in the notification area states that Windows Defender is checking for definition updates. c. If Windows Defender reports a failure to update definitions, see the "More Information" section, and then follow the Windows Update troubleshooting information.

Back to the top

Definitions are files that behave like an encyclopedia of known spyware and other potentially unwanted software. Because spyware is continually being developed, Windows Defender relies on up-to-date definitions to determine whether software that is trying to install, run, or change settings on the computer is potentially harmful.

Windows Defender works with the Windows Automatic Updates feature to automatically install the latest definitions. To turn on Automatic Updates, use one of the following methods.

Windows XP and Windows Server 2003

1.	Click Start, click Run, type wuaucpl.cpl, and then click OK.
2.	Click Automatic (Recommended), and then click OK.

Windows Vista

1.	Click Start, click All Programs, and then click Windows Update.
2.	In the left pane, click Change settings.
3.	Click to select Install updates automatically (recommended).
4.	Under Recommended updates, select the Include recommended updates when downloading, installing, or notifying me about updates check box, and then click OK. If you are prompted for an administrator password or for confirmation, type the password, or provide confirmation.

Windows Update troubleshooting

To troubleshoot a potential Windows Update problem, follow these steps:

1.	Visit the following Microsoft Web site: http://v5.windowsupdate.microsoft.com/windowsupdate/v6/troubleshoot.aspx (http://v5.windowsupdate.microsoft.com/windowsupdate/v6/troubleshoot.aspx)
2.	On the Options Web page, enter keywords that describe the problem. If you cannot resolve the problem, go to the next step.
3.	Visit the following Microsoft Web site for more information about how to resolve this problem: http://go.microsoft.com/fwlink/?linkID=25127 (http://go.microsoft.com/fwlink/?linkID=25127)
4.	Examine the %systemroot%\Windowsupdate.log file for error messages, and then search the Microsoft Knowledge Base for more information about errors in the Windowsupdate.log file. To search the Microsoft Knowledge Base, visit the following Microsoft Web site: http://support.microsoft.com (http://support.microsoft.com/)
5.	After you resolve this problem, click Check for Updates on the Windows Defender home page.

If you are in a corporate environment, a network administrator may be blocking access to Windows Update. Or you may have a network configuration problem that relates to third-party products. Contact the network administrator for more information about how you can update definitions for Windows Defender.

In a corporate environment, a network administrator may have deployed the Microsoft Software Update Services server on the network. For example, the network may be using Software Update Service (SUS) 1.0. However, Windows Defender cannot receive updates from SUS 1.0. Contact the network administrator to determine whether this is the problem. In this case, the network administrator must deploy Windows Server Update Services (WSUS). Definitions for Windows Defender must be offered from the WSUS server.

For more information about WSUS, visit the following Microsoft Web site:

Back to the top

Technical support for x64-based versions of Microsoft Windows

If your hardware came with a Microsoft Windows x64 edition already installed, your hardware manufacturer provides technical support and assistance for the Windows x64 edition. In this case, your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation by using unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with a Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware. If you purchased a Windows x64 edition such as a Microsoft Windows Server 2003 x64 edition separately, contact Microsoft for technical support.

For product information about Microsoft Windows XP Professional x64 Edition, visit the following Microsoft Web site: For product information about x64-based versions of Microsoft Windows Server 2003, visit the following Microsoft Web site:

Back to the top