Hi,
CPU usage will go high, if there are some unnecessary applications get loaded with the operating system.
I would suggest you to perform following steps and check.
Method 1: Run System Maintenance troubleshooter and check if it helps.
Follow the steps:
a) Press Windows and X key together and select
Control Panel.
b) Click on Troubleshooting.
c) Click on View all option on the left side of the Windows.
d) Click on System Maintenance option.
e) Click on Next and follow the onscreen instructions to troubleshoot the issue.
If the issue still persists, continue to the next method.
Method 2: We will check the functionality in safe mode with networking.
Step 1: Start your computer in safe mode with networking and check the CPU usage.
Refer this link to start the computer in safe mode.
http://windows.microsoft.com/en-IN/windows-8/windows-startup-settings-including-safe-mode
If it works fine in safe mode with networking, let’s perform clean boot.
Step 2: Perform clean boot.
Clean boot will help us identify if any third party applications or startup items are causing the issue.
To do this, follow steps from this link:
http://support.microsoft.com/kb/929135
Note: After checking the functionality in clean boot, follow the suggestions under “How to reset the computer to start as usual after troubleshooting with clean boot”.
Hope the information provided is useful. If the issue persists, reply here and we will be glad to help you.