PC has slowed down-antivirus problem need help

Hello,
My PC has suddenly slowed down. I think it is because of my anti-virus. I have recently installed Kapsersky internet security and since than It is working like an old man. I do not what to do.
Is there a way to solve this problem.
I need the internet security since use the internet a lot.
Kindly someone help me out of this problem.
Arnold Huang
