McAfee Anti Virus makes my computer slow

Hello! Everyone,
I have a problem with my Antivirus program. I hope somebody can help me. My computer is running on Windows Vista SP2. My HDD is 40GB, 2.0GHz. Even though my HDD is only 40GB, I do not have much files in my computer as well as applications because I am using my computer mostly on the internet. Now, my Antivirus software is McAfee.
At first, I thought my browser is what makes my computer slow. so, I cleared cache, cookies, files and histories on my internet options. Unfortunately, the same slow connection persisted. Then I decided to check my "Task manager". That’s when I realized that McAfee consumes a lot of memory in my active processes.
When I tried to exit McAfee, I don’t experience a slow connection. Is there something I can do about this without removing McAfee?
Or do I really need to get rid of it.
Appreciate if somebody can help.
