@
Mondriaan - if CCleaner and other programs wont run properly, and can't be killed with Process Explorer, and the latest calibre wont install then I think something is is very wrong with your Windows installation
My suggestion is to reinstall Windows, you might be able to do an
Inline Repair Install That will preserve most applications and Windows functions and customisations, that link has full details.
If you are using the 64bit version of calibre, you could try installing the 32 bit version, they can coexist and they will use the same configuration data and see same libraries. Your other choice is to use the portable version of calibre.
BR