Looks like it is working correctly to me.
Close all apps, and show the CPU activity.
Also, download and run Download Intel® Processor Diagnostic Tool
And, you did not provide what OS you are running, and your computer/motherboard model number. If you are using Windows 10, you should note that your processor is not supported.
I closed all programs and the attached is what I get.
Sorry forgot to mention:
Intel i5 750 @2.67GHz
I ran diagnostic and all passed but I didn't think that all cores would have operated at the same time at the same amount.
Capture.PNG 35.5 K
The second chart is what I would expect from an idle state.
As I mentioned, your processor is not supported on Windows 10.
This message was posted on behalf of Intel Corporation
Your CPU usage looks healthy; however, I have to second on what Doc mentioned, your graphics controller does not support Windows® 10. The CPU usage may vary if the operating system is not supported, especially since there are no drivers that can manage the resources for the CPU, chipset and other components.