How do I find out what program is using all my CPU?

All evidence to the contrary, computers can really only do one thing at a time. OK, a dual core or dual processor machine can do exactly two things at a time, a quad core can do 4, and so on. But a single CPU can do exactly only one thing at a time. It just switches between them all really, really quickly.

So when one program needs all of the CPU's attention, other programs that need the CPU might not get enough time to do their work. That typically results in a very slow system, from a user's perspective.

We can use task manager to figure out who the culprit is, but I very much prefer the free download Process Explorer. Download and run it, and you should see something very much like this:

The default display shows all he tasks running on your computer, in hierarchical order, meaning that if program A was the one that started program B, then program B appears indented beneath program A. That can be helpful for other reasons, but not what we want here.

Click on the column labeled CPU, and Process Explorer will sort the processes by CPU usage. The processes using the most CPU will be listed at the top:

Here you can see that when I took this image my CPU was actually 68% idle; in other words the it was doing nothing at all two thirds of the time. The next highest program on the list was SnagIt, the screen capture program I use, using about 14% of CPU, followed by Windows Explorer, Trillian, and others in decreasing order.

"In many reports I get it's a program called 'svchost.exe' that has people concerned and mystified."

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How do I find out what program is using all my CPU?

very nice ,informative post Jan :)