It is verifying the blocks it download, of course it use the cpu. Is it a problem that your computer is actually used? Because that is why computers exist: to be used.
So it is normal. Thanks for the information. The problem is that I want to use my computer to do other things in the meantime, which at times can be affected by overall CPU usage of course.
Anyway, I tried Multibit and like its convenience. Will check out Electrum. Thanks.