Webroot Secure Anywhere version 18.104.22.168 didn't care and started the automated cleanup engine without even asking me and *tada* removed c:windowsexplorer.exe because of a wrong MD5 hash. Immediately the taskbar was gone as well as my desktop. Some moments later the whole system crashed with a blue screen. Since I use Windows 7 I cannot remember that I ever saw a blue screen.
I had to restart the PC and after the Windows login the whole screen was just black and a lovely "explorer.exe Class not registered" error message appeared. So no start button, no file manager... nothing.
The first thing which came to my mind was to check the quarantine but as I mentioned, the taskbar was gone. No way to manually open Webroot. In task manager it was running but no way to open the UI.
The second thing I tried was a system restore. Thanks god I did one the day before and thanks god I knew the file name of the system restore program. So not much was lost. It worked. Webroot of course was gone. I re-installed Webroot... and exactly the same problem again. explorer.exe deleted, and desktop as well as taskbar gone.
How to fix it:
The bad thing: The modified explorer.exe is gone and the original one is back. So one gets back the ugly Windows theme without any customization.
Seems it is new that Webroot "complains"well deletes would be better) about modified explorer.exe files. When I used Webroot last time, it did not complain at all.
Anyway, dear Webroot team: Please do NOT auto delete files. Please ASK the user first. Auto-deleting files is a no-go for me. Thanks god I remembered the important file names like sfc.exe etc.