my windows defender not opened please tell me how solve this problem?

What errors are you getting? Do you have another anti-virus/firewall program installed? If you do, uninstall it and try to launch Defender.

Hi,

Could you please tell me whether the problem occurred suddenly and you use it normally before? We would like to know the event log for the issue. You can use the Event Viewer to send the event log to us. Before we know that, we cannot conclude the exact reasons for the issue.

https://support.microsoft.com/en-us/kb/308427

However, you can attempt to follow the suggestions below to troubleshoot the issue.

Firstly, scan the virus in safe mode due to the virus may block the module of anti-virus software, then start Windows Defender in clean boot mode to check whether existing conflicting software. Disable or uninstall the 3rd party anti-virus for test. This is the way to exclude the possibility of conflicting problem.

Secondly, press Windows key + R and then type services.msc, then find the service called Windows Defender service and restart it.

In addition to that, use SFC to repair the system components to in case of the system files corrupt leads to the issue.

https://support.microsoft.com/en-us/kb/929833

Also, you can troubleshoot the issue by yourself according to the error message by referring the link below. 

http://www.thewindowsclub.com/windows-defender-is-turned-off

Best Regards

Simon

• Edited by Simon_Wang__ 22 hours 12 minutes ago

Hi,

Could you please tell me whether the problem occurred suddenly and you use it normally before? We would like to know the event log for the issue. You can use the Event Viewer to send the event log to us. Before we know that, we cannot conclude the exact reasons for the issue.

https://support.microsoft.com/en-us/kb/308427

However, you can attempt to follow the suggestions below to troubleshoot the issue.

Firstly, scan the virus in safe mode due to the virus may block the module of anti-virus software, then start Windows Defender in clean boot mode to check whether existing conflicting software. Disable or uninstall the 3rd party anti-virus for test. This is the way to exclude the possibility of conflicting problem.

Secondly, press Windows key + R and then type services.msc, then find the service called Windows Defender service and restart it.

In addition to that, use SFC to repair the system components to in case of the system files corrupt leads to the issue.

https://support.microsoft.com/en-us/kb/929833

Also, you can troubleshoot the issue by yourself according to the error message by referring the link below. 

http://www.thewindowsclub.com/windows-defender-is-turned-off

Best Regards

Simon

• Edited by Simon_Wang__ Monday, August 31, 2015 9:12 AM