Windows Defender

Click the Windows Start Menu icon in the bottom corner of the screen. Once "Open" and go to your computer's Control Panel.

Select "Windows Defender" from the available icons. This opens the main Windows Defender interface.

Choose "Tools" from the top of the screen. This takes you to the main Windows Defender control list. Select "Options" from the list.

Scroll down to the bottom of the list. Uncheck the box that says "Use Windows Defender" and click "Save." A confirmation box will pop up so click "Continue" to move past it. One last box will appear telling you that Defender is turned off (and that it doesn't think that was a good idea).

Turn Windows Defender back on by opening it up in the Control Panel. A notification will appear telling you that it is turned off. Select "Turn On and Open Windows Defender" to enable it.

Open the Windows Defender program in Vista by clicking "Start," "All Programs" and "Windows Defender." If you have Defender on your desktop, use the icon there to save time.

Look at the menu options at the top of the page and select "Tools."

Access all of the options for Windows Defender by clicking "Options" in the drop-down list.

Find and click "Administrator Options" to control how Defender protects your computer.

Remove the check mark from the box next to "Use Windows Defender" to disable Defender in Vista. You may see a warning screen referring to a lack of security created by this change. Windows Vista may ask for an administrator password to disable Defender.

Apply the change made to disable Defender by clicking the "Save" button.

Open Windows Defender and go to the "Options" page. Simply click on the following: "Start," "All Programs," "Windows Defender," "Tools" and "Options."

Scan down the list of options to select "Real-time Protection Options."

Select the "Use Real-Time Protection (Recommended)" box to choose the limitations you want to place on Windows Defender. Remove or place check marks next to the options you want Defender to follow.

Use the "Save" button to apply the changes you make to Windows Defender.

Download the updated definitions by pointing your browser to the following URL: http://go.microsoft.com/fwlink/?linkid=70631. Choose to save the file to your hard drive, and allow the download to complete before continuing.

Open the folder that you saved the definitions file to. If the computer is a Windows Vista-based system, open it by right-clicking on the file, then selecting "Run as Administrator." Otherwise, just double-click it.

Wait while the definitions installer automatically updates Windows Defender. A progress bar will appear on the screen letting you know how much time is remaining. Once it has finished, the installer will close without further notification, and the definition update is complete.

Click "Start," then "All Programs" and "Windows Defender."

Click "Tools" and "Options."

Scroll through the list of options and remove the checks from the boxes called "Use Real Time Protection" and "Use Windows Defender."

Click "Save." After the saving the changes a pop-up will notify you that Defender has been disabled.

Click "Start," then type "msconfig" into the search field and press "Enter."

Click on the "Startup" tab in the system configuration window.

Find Windows Defender in the list, remove the check, click "Apply," then click "OK." This will make it so that Defender does not start up when you start up your computer, and should increase boot speed.

Click "Start," then "Control Panel," and double-click "Add/Remove Programs."

Search the list for Windows Defender, and double-click it.

Confirm that you want to remove Windows Defender from your system, and wait for the auto uninstaller to complete.

Restart your computer.

Click "Start," then "Control Panel," and double-click on "Windows Defender."

Click on the menu called "Tools," then click "Options," which will appear under a heading called "Settings."

Scroll down to the bottom of the options list, and uncheck the box called "Use Windows Defender."

Click "Save." Windows defender will be disabled; a notification should appear confirming the change.

Click "Start," then click "Run."

Type "msconfig" into the Run field and press "OK." In Vista you can type "msconfig" into the search bar and press "Enter."

Click on the "Startup" tab of the window that opens.

Find Windows Defender in the list, uncheck it, click "Apply," then click "OK." On your next restart, Defender will not boot up.

Click "Start." Then click "Control Panel."

Double click on "Windows Defender." The icon for defender looks like a gray brick castle wall.

Click on the "Tools," menu. Then under a heading called "Settings," click "Options."

Scroll down the options menu until you see a heading called "Administrator Options."

Check the box called, "Use Windows Defender." Then click the "Save," button to save the changes. You may also wish to check other boxes in the options menu to activate other features, such as automatic malware scanning.

Navigate to the Windows Defender Beta download page (see Resources).

Click "Get it now" on the main page. Select the speed of your Internet connection and click "Download." Click "Run" to begin the download process. When it is complete, an automatic install window will open up.

Click "Next" and click "Validate" to validate your genuine copy of Windows. Read the terms and agreements, then click "I accept."

Click the "User recommended settings" download check box and click "Next." Click the "Complete" radio button and click "Next."

Click "Install" to complete the process. Launch Windows Defender Beta.

Click "Start" and "Control Panel"; then double-click "Windows Defender."

Click the "Scan" button to run a total system scan with Defender.

Wait for the scan to complete; then click "Tools" and deselect "Options."

Check the box labeled "Automatically scan my computer" under automatic scanning if it is not already checked, and then select times for scans using the drop-down menus. Scroll down the options menu and make sure the "Use Windows Defender" box is checked.

Click "Save"; then close the window.

Click the Windows "Start" button and click the "Control Panel." Double-click "Add or Remove Programs" to open the Programs window.

Scroll down the Programs window and click "Windows Defender." Click "Change/ Remove" and click "Yes" to confirm and remove it from your computer.

Double-click "My Computer" on the desktop and double-click the "C:" drive. Double-click the "Program Files" folder. Locate the Windows Defender folder and right-click it. Click "Delete."

Empty the recycle bin and restart your computer.

Disable Windows Defender and prevent it from launching. In Windows Vista, you can only disable this program because it is installed by default on the operating system. To disable it, click the Windows "Start" button and click "Start Search."

Type "services.msc" (without quotes) and press "Enter" to open the Services console.

Scroll down and right-click "Windows Defender." Click "Properties."

Select "Disabled" under Startup Type and click "Stop." Click "OK" to save the changes and restart your computer. Windows Defender is shut down and deleted from the system tray.

Go to the Windows Defender web page, and click "Get it Now" if you do not already have it installed on your computer. Click "Download" and click "Save" to download the installation file on your desktop.

Double-click the installation file, and click "Run" to launch the installation wizard. Follow the guided instrucitons to install the program on your computer.

Click the Windows "Start" button, and click "All Programs." Click "Windows Defender" to launch the application once the installation is complete.

Click the "Check for updates" button. Windows Defender checks the Microsoft server for new spyware and virus definitions and installs them automatically. The alert shield turns into a green check mark when the update process is complete.

Click the "Tools" button on the main menu, and click "Options." Adjust the automatic scanning settings in the "Automatic Scanning" section. Select the frequency to scan for threats and the time of day to scan the computer. Select the scan type (Quick or Full).

Click "Microsoft SpyNet," and specify whether you want to join the online community. Select "I don't want to join Microsoft SpyNet at this time" if you are uninterested.

Select the "Use realtime protection (recommended) check box. Real-time protection alerts of malicious programs attempting to install themselves on your computer. Select all the options under real-time protection.

Select "Advanced" in the options console, and select the "Scan the contents of archived files and folders for potential threats" check box. Click "Do not scan these files or locations," and click "Add." Specify the locations you do not want Windows Defender to scan.

Click the "Quarantine" link, and select the programs to place or remove from the quarantine vault. Run system scans once you complete the configuration process.

Log on to an administrator-type user account in Windows Vista.

Click the Windows "Start" button and open "Control Panel."

Choose "Security" and click "Windows Defender."

Click "Scan" in the Windows Defender window to scan your computer.

Click the "Start" button, then click "Control Panel."

Double click "Windows Defender." If you do not see this option, click "Classic View" in Windows Vista or "View by: Small Icons" in Windows 7.

Click the "Tools" button at the top of the screen, then click "Options."

Click the "Administrator" link on the left side of the window.

Remove the check from the box labeled "Use Windows Defender."

Click "Save," then click "Close." Note that you may need to enter the Administrator password for your computer to complete this action. Windows Defender is now disabled.

Uninstall Windows Defender. Open your Control Panel and select "Add/Remove Programs," then pick "Windows Defender" from the list. Click "Uninstall."

Reinstall Windows Defender from a fresh file. Download the program from Microsoft's site, then open and install it. Open the program after installation is finished.

Make sure that you don't have another firewall running that has blocked Windows Defender. If you have another firewall program installed, check the settings and make sure it is switched off, then try opening Windows Defender again.

Check your Internet connection. You may not be connected to the Internet when you are trying to update. If this is the case, turn your Internet connection on and try updating Windows Defender again.

Make sure that your settings are set to update from Windows Update rather than Microsoft Update. Click "Start," "All Programs," then select "Windows Update" to check. If Microsoft Update opens instead, click on "Change Settings" on the left side of the window, then uncheck the "Use Microsoft Update" option.

Download updates directly from Microsoft's website. Downloading from the website may work better because it is the direct source. After the download is complete, open the file and let it install itself.

Check your Internet connection. If you are not connected currently, you will need to reconnect to the Internet to get the update. Reset your modem and make sure your router and Wi-Fi are on, if you use them. If your Internet still won't connect, contact your Internet service provider.

Set your computer to receive updates from Windows Update rather than Microsoft Update. Click on "Start," then open your "All Programs" menu. Select "Windows Update" from the list and navigate to the "Change Settings" option. Once there, uncheck "Automatic Updates," "Recommended Updates" and "Use Microsoft Update Service." Restart your computer and run Windows Defender again.

Download an update program from Microsoft's website. This program will force Windows Defender to update. Install the program, then open Windows Defender to allow it to update.

Empty your temporary Internet files and cookies. To do this, find your System Tools folder in your All Programs list. It is typically located in the Accessories folder. Within the System Tools folder, select "Disk Cleanup" to remove these files. When the Disk Cleanup window opens, select the files you would like to delete, then click "OK."

Update the Windows Defender definition pack. Open Windows Defender, then click the "Update" link to get the most up-to-date malware definitions.

Allow Windows Defender to run with minimal other programs running. Having too many programs going at once can overload your computer system and therefore slow the scanning process down. Keep the number of programs running during a scan down to only the essentials.

Download and run Microsoft Installer CleanUp Utility (see Resources). This download will fix a corrupted .dll file that is preventing Windows Defender from uninstalling. After running the program, Windows Defender should be able to be uninstalled.

Use Run to uninstall Windows Defender directly if the .dll fix doesn't work. Click your "Start" menu, then click "Run." In the Run window, type "msiexec /uninstall windowsdefender.msi /quiet /log uninstall.log" and click "OK." This will uninstall the program, but only for users running Windows XP.

Use a third-party uninstallation program, such as Revo Uninstaller (see Resources), to try to force an uninstallation for users not running XP. Download the program, then install it and select Windows Defender from the list of programs that can be uninstalled. Allow the program to remove Windows Defender. You may have to restart your computer for it to uninstall completely.