Sometimes i get bizarre CPU usage in Win 7. I could be doing something as simply as surfing the net, but my i5-2410m is running at full speed; 2.7GH / 2.9GHz. I look at task manager and FireFox is fluctuating between 1% to 8% CPU usage. Some background programs fluctuates between 0% to 4%. The CPU does not seem to be doing anything that requires it to run at full speed and thus cause the fan to ramp up to full speed.
As a temporary fix I put the laptop into power saving mode where the maximum CPU usage is 0% (under Advanced Power Settings). Annoying, but i can't find any other solution so far.
You can download a widget call All CPU Meter which is what I use the monitor CPU usage and CPU temps. You will need to install Core Temp though to monitor the CPU temps. You can download the widget and Core Temp in the following link:http://addgadgets.com/all_cpu_meter/