Windows Defender cannot be opened under Win7 Cause

Windows Defender, formerly known as Microsoft AntiSpyware, is a program for removing, isolating and preventing spyware. It can run on Windows XP and Windows Server 2003 operating systems. Built into Windows Vista and Windows 7.

In Windows 7, Windows Defender's notifications are shorter, have more scanning options, and have less impact on the performance of your computer. A new feature called Clean System provides the ability to clear all suspicious software with a single click.
Now, Windows Defender is still part of the operations center. The simple new design keeps the PC running smoothly. All notifications from Windows Defender are sent through the operation center.
Normally, you can open it by clicking Windows Defender in the Control Panel. Recently, I have encountered such a problem: Click Windows Defender, a dialog box pops up:

This program is closed

If you are using other programs to check for harmful or unwanted software , use the Operations Center to check the status of the program.

If you wish to use this program, please click here to open it.

Go to the operation center, click Enable, pop up a dialog box like the previous one, click on the "Click here to open it" long time, a dialog box pops up, saying that due to the operation time has passed , the operation returns, error code: 0 * 800705b4

Why can't Windows Defender be used?

Later, referring to Microsoft's official documentation, it was discovered that MSE was installed. Because the MSE already contains all the functions of Defender, it can even be said that some components in the MSE are Defender, so after installing MSE, Defender will be automatically disabled. This is normal, no need to worry.