My pc wont run fast.. cpu usage always at 100%!?

My dear friend most probable cause of your problem is a Virus attack. So format your system as fast as possible for a trouble free operation.

Well, when you start it up it's going to be 100% because it's loading all of your computer services. It should taper off after a few minutes; if it doesn't it means you have a bad program running that's sucking up all your system resources. Check online to find out what processes and services your absolutely need to run and adjust start-up programs and services accordingly. Don't run software like Limewire or BearShare as they often leech system resources and allow for malicious code to be executed on your computer. Also, defragging your disc will help speed up your computer by arranging data to flow more smoothly so try that as well. If all else fails, adjust windows display properties to disable transparency effects and transitions to help boost performance. If using Windows Vista make use of the ReadyBoost feature to help take pc load off internal parts and check your device manager to make sure you do not have any conflicting devices.

Go to Task Manager and then in the processes tab. Sort the processes by CPU usage. It will help you to know it least what is taking up most space. If nothing of your own or a malicious application then it means the system is taking up more and then you have to optimize your system by uninstalling applications which incorporate background processes.

Check your computer for viruses. Do you have to many programs installed or to many windows open at once? How old is your laptop? Maybe it's time to upgrade your pc. Or just try restarting your computer and see if that fixes anything.

Try increasing the amount of ram or buy another computer

in folder option(control panel), don't check on view thumbnails for media file. restart to take effect

cause it is windows