System Monitor II

System Monitor II is a free desktop gadget for your windows which checks memory usage and core CPU usage in real-time and lets you monitor system performance.

It can display the system's overall memory usage and CPU usage of each core in a multi-core processing environment. It has the ability to show the percentage usage and temperature of each of the core associated with the processor, which makes it better than the windows default Task Manager. So whether you have a single core, dual core, quad-core, 10-core, or even higher core processor, you can monitor the percentage usage and temperature of each independent core through this powerful application.