With active real time antivirus hard file is constantly running

Downloaded CIS latest version. Now if real time antivirus is active, hard file is constantly running. Cmdagent.exe shows about 25% CPU activity while this is happening. I’m not concerned so much about the CPU hogging as I am about wearing out my hard drive. I can stop it by disabling real time AV but then I am vulnerable to virus. Currently I am operating with Comodo real time AV disabled and using AVG Anti-virus free. The Comodo firewall is still in Clean PC mode but I would like to use the full Comodo suite as I have had good luck in the past with Comodo AV and firewall. The firewall seems to have no effect on this problem.

Is this a clean install of CIS or did you install on top of an older version?

May be it is reacting to other processes running like indexer? What OS are you on?

It is a clean install. I am using XP. There were other processes running but I shut down everything and the only thing that affects the hard drive is the Antivirus. Shut it down and there is no problem.