Can it be that I don't have an activity monitor
Everybody should have it, are you saying it's not inside the Utilities folder inside the Applications folder?
yes it is not there.
then extract/install what you need from your Install Disc.
Which OS do you have?
What is the history of your Mac?
I have found that if you run the App "Live Wallpaper" it will cause your MBP to run a bit warm. Just my .02
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