Win7 64bit install is impossible

Today, my LibreOffice has informed me that a new stable version (5.0.6) is released.
So I download it from the official site, but every time I tried to install, the installer asked me to close programs which are supposely using files needed to be updated.
I close the programs but installer keep asking using now numbers (PID, I suppose).
These PIDs correspond to nothing in the TaskManager.

My actual configuration is :
Windows 7 64-bits Professional edition
Java 1.8.0_91 (32-bits)

Have you tried a fresh install?

I have uninstalled LO 5.0.5, with CCleaner.

It worked, although the uninstaller asked me to shut down the Windows explorer. I’m not afraid to do so, because I’m familiar with computer, but that’s weird. Is there an explanation?

Finally, the fresh install worked without any other closing request.

I use CCleaner and have never had a request to close W/Ex when uninstalling.