I try to start up my windows defender on my Windows Vista basic computer many times and I get an error Ox800106ba every time. I try restarting my computer and seeking Help & Support. So far both of them didn't work. Can you help me out? Thanks.

Thank you for using the Microsoft Windows Vista Security forum. My recommendation is that you not turn off Windows Defender. That having been said there is a way to turn it off but is involves editing the Registry. You edit the Registry by clicking the start Orb, clicking All Programs, Accessories, Run. Type regedit and click ok. Inside the Registry Editor navigate to the key you wish to edit. Modifying REGISTRY settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of REGISTRY settings can be solved. Modifications of these settings are at your own risk.. Policy setting: Turn off Windows Defender Registry key name: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender \DisableAntiSpyware Policy description: Turns off Windows Defender Real-Time Protection. No more scans are scheduled. If you enable this policy setting, Windows Defender does not run. Computers are not scanned for spyware or other potentially unwanted software. If you disable or do not configure this policy setting, Windows Defender runs, and computers are scanned for spyware and other potentially unwanted software. I hope that this information is useful. Once Windows Defender is tuned off, you can use Microsoft Security Essentials (If you have an antiviruse and an antispyware, you will not need to install it): http://www.microsoft.com/security_essentials/ If you install it you will not need to use windows Defender. Remark: Windows Defender may be in conflit with an antivirus like McAfee and this may be a possible cause of your problem. This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.

Hi, Please first check the Windows Defender service is set to Automatic. Click start, type services and press enter. From the service list, please locate the Windows defend service, double click to open the propertis windows. Make sure the startup type is set to automatic. If this did not help, I would suggest prepare clean boot to troubleshoot. Clean Boot prevents software conflicts by preventing the startup items and non Microsoft services from loading. This way you can safely follow the process of elimination to check which application is causing this behavior. Refer: How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7 http://support.microsoft.com/kb/929135 Note: Ensure that you put your computer back to normal startup mode after completing the troubleshooting steps. Steps are available in the article given above. Please tell us the result. Regards,Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Go to the main Windows Update window and click on "Installed Updates", and then remove "Update for Microsoft Windows (KB931099)". Reboot it. Go back to Windows Update, and re-install the same update, by clicking on the Check for Updates button. This should essentially re-install Windows Defender on Vista.