high computer slow render blender Man that is insane.

I using blender 2.77 and start to study how to process an image for a web site.

400x600 pixels 160 images

This is using 100% of my processor and i have an

I7 3.40 ghz 8 memory and Nvidia 660 TI

Why it using 100% to this size of image?
It is normal and logical that Blender use all available cores and CPU time for render. You have two options for change it. 


You can set low priority in system task manager (how to do it depend on system you are using, this is about system, not about Blender)
You can set number of used cores for render.


EDIT: actually point one does not change percentage of usage, only set low priority, so your CPU will work on 100%, but will preferentially prioritize other running programs ans services