You should use the resource monitor type options.
During your actual play, they'll let you know what percentage of your resources you're actually using.
Anything that is close to 100%, or occasionally hits that 100% is a bottleneck.

An upgrade to a bottleneck will improve your performance.



Control + Shift + Escape (Win 7).
Performance Tab.
Resource Monitor Button.


You could also try free download utilities.
CPUID HW Monitor, will let you check the temperatures of your CPU.
GPU-Z, will show the percentage load of your graphic card, and the operating temperature.