Sounds like you must have a lot of start up programs which are consuming your CPU. Many new machines come with all sorts of rubbish loaded by the maufacturer some of which phones home or runs in the background unrequired.
Start by going through the programs and get rid of ones you do not need and stop those you do not need at start up. You can always start them when you need them.
If you run the sidebar use this to keep an eye on what is happenning.click here