@Hugo Chavez Frias

Run TASK MANAGER - CTRL + ALT + DEL - select "Start Task Manager"
You probably won't see anything in Applications but Select the process TAB - third column is the CPU usage - if you have nothing running on the machine, then probably the top usage will be "Task Manager" - if there is something using CPU continuously you need to check what it is "GOOGLE" or other search engine.

Then try the "Performance" TAB and see what your usage is like - there is a "Resource Monitor" Button at the bottom. If anything is using more resource than "Resource Monitor" or your Virus Checker then check out what that is.
Word of Caution if your browsing for application names you will get a load of adverts for "Scan your machine" - "Optimise your PC" - don't go there !!