Windows key+L should do what you need.
Use Windows+L. If you use AutoHotKey you can reprogram Windows+L to do other things too, like lock your session, and also wait 10 seconds and put monitors to sleep. Powerful little hotkey program.
Also, Ctrl+Alt+Del, Enter and Ctrl+Alt+Del, Alt+K seem to work for me.
You can even use a simple batch file. Just double click on it & your PC will get locked.
Just copy & paste the below code in to Notepad & save it as (for example) “lock.bat”.
That’s it – you’re done, just double click on it.
The code is:
@echo off rundll32.exe user32.dll, LockWorkStation cls