My Computer is Going REALLY SLOW I don't know what to! Please Help My CPU Usage is at 100% all the time!?

My Computer is Going REALLY SLOW I don't know what to! Please Help My CPU Usage is at 100% all the time! I followed some tutorial on youtube that was supposed to speed up my system shut down and start up speed, Instead It slowed it down like 50x so I undid the settings and its still going slow plus before that my computer has been Going slow for the past 3 months and my laptop is Fairly new about 1 year old Dell won't help they just ask for $200 which i dont have so I cant get it fixed. I have A Laptop dell studio 1558 windows 7 home premium and an intel CORE i3 Which is supposed to be really fast but its not. please help and for some reason every program always freezes up every time I open it. Will System restore to factory settings help? Do I just need to reset all settings and not data? PLease be EXPLICIT with your answer. Thank You.