Hi, you may try the following steps, which also mentinoned how to do when you can't opend the task manager.
1.Open Task Manager
Open the task manager, which may seem impossible to do since the Start menu isn't showing up. Don't worry: Windows comes with keyboard shortcuts. Press "Ctl," "Shift" and "Esc" to bring up the task manager. Here you'll see a list of the programs you have running, which will not include Windows Explorer (explorer.exe) because it's crashed. So start it again.

2.Start Windows Explorer
Click the "Applications" tab, if it's not already selected. Then press the "Create New Task" button, which will allow you to run any program you wish. Type "explorer.exe" into the resulting window and click "OK." Windows Explorer will start up again, bringing your desktop back to full functionality.

3.Alternatives
If, for whatever reason, you cannot launch the task manager, there is another way. Hit the "Windows" button and the "r" key at the same time to bring up the "Run" dialogue. Then type "explorer.exe" and your computer will become usable again. If this doesn't work, hit "Ctl," "Alt," and "Delete," then click "restart computer." If Windows Explorer does not launch after rebooting, it may be time to seek help from a professional.