That CPU percentage is not efficiency, it is utilization.  At 100% it means your systems processor is using all of its capability to perform whatever tasks it has to handle.  Are you letting the system handle the swap file or are you setting it manually?  You really want that CPU usabe to be as low as possible before you start up carrara.  Turn off all non essential programs and see if that lowers the percentage so that when you start Carrara, it has more availlable capacity for it.

Quote - Good morning,

I'm back home and tried to render again. Well, the results were the following according to the task-manager:
CPU efficiency 100%
swapfile 0,99 - 1GB

Have I checked the right facts? 
Actually, right before the application shuts down, the kernel-times increased up to 50% of the CPU efficiency.
Perhaps I should stop importing several car. files with models I've completed before and instead load them as objects from the browser. Well, I'm already recreating the whole scene and hopefully it ends up well when rendering.

~Sassy~