cpu usagepowerthinkpadwindows 7
Computer/Laptop: Lenovo T500
When I leave my PC, it turns off the display after X minutes. That's fine.
However, since I use "Proccess Explorer" (SysInternals) there is a bit of a history in my tray about the CPU usage. The usage goes UP. (I also notice the fan gets louder when I leave my PC there for some reason, like a download / rip radios, whatever.)
Why is that?
(I'm using the hybrid ATI+Intel drivers by Lenovo. Latest at the moment.)
Windows 7 has "Power Options" that could be affecting your performance. To check for this click on the start button, go to control panel, and click on "Power Options."
Now, make sure that the "Show Additional Plans" button has been selected, if it has, it will say "Hide additional plans." Click on the "High Performance" power plan. You can also go into the plan and change settings for optimal performance.
I've found such problems before; as others have said, it was often due to HDD failure, but also I've seen it with Windows XP on a solid-state HDD in a HP Mini 110 netbook, some years ago. When the disk was busy writing, the whole thing would often be quite unusable. The problem did not manifest with other OSes, such as Ubuntu, and I can't say about Windows 7.
It may be worth looking for a driver update or trying a different OS (even from a Live CD or similar).
In Windows, it is useful to look at the Performance Monitor (as distinct from the Resource Monitor), and in the Performance > Monitoring tools > Performance Monitor tree, add (green plus icon) and under the Physical Disk part of the tree, add the entries that relate to the Queue Size. I suspect you'll find that one of your disks will have a queue size that is often very high for long periods of time.
Best Answer
Your computer is possibly running Scheduled Tasks that are set work when the system is idle, for example, defragging in the background.
Note the "Start this task only if the computer is idle for" parameter in the screenshot.
In the Task Scheduler, I would also try clicking on the "Display all running tasks" in the right pane. I am not sure if one of these idle tasks will show there, but it might.