Win10 windows defender can not start the solution

Recently, many friends have encountered a very troublesome problem in the process of using Win10 preview version. The problem is as follows: When using other third-party security software and uninstalling, want to change After returning to the Windows Defender that came with the system, I was surprised to find that it could not be opened. After opening, the system will pop up an error prompt window, as shown in the figure below.

win10 windows defender can not start the solution:
1. According to the error message, we first suspect that the application corresponding to the Windows Defender service has been tampered with by third-party security applications. You can query the application corresponding to the Windows Defender service by using the “Windows logo key+R” to open the Run window and entering “services.msc”; or by using the “tasklist /svc” command in the Command Prompt window. program.
After querying, we can see that the application path corresponding to the service is "C:Program FilesWindows DefenderMsMpEng.exe", and it is not possible to start the service by clicking Start, or to display the operation after clicking, but still can't Normal use, the error remains.

▼ In the "Windows Defender Service" service, we use the “tasklist /svc” command at the command prompt to view the service and program dependencies as follows. The service PID process number is 2664, which corresponds to the "MsMpEng.exe" file.

2. However, after finding the corresponding application, we found that it has not been tampered with by comparing it with the certificate of the normal “MsMpEng.exe” file.

3. Windows Defender original file is no problem, but gives such an error message, and can not open the service through the normal service management page. This problem is probably a bug in the current Windows 10 operating system. To solve this problem, right click on the “Start button” and select “Command Prompt (Administrator)”, enter the following command, and then press “Enter].
“sc start WinDefend Enable” (without the quotation marks on both sides)

Then, let's take a look at the Windows Defender that prompted the error before it can be opened normally.