Is COMODO Defense+ all I need? Because I’m looking for a antivirus that has NO impact on system resorces and decided to install COMODO CIS 3.9 but just the firewall and Defense+. I have Defense+ set to Safe mode. THANKS!
G’day and welcome to the forums.
I would recommend using the AV in conjunction with Defense+.
The additional system overhead in initializing the AV engine, and its subsequent impact on system resources is negligible - I can’t spot the difference at all. 
Try it yourself. The AV component can be easily added or removed by re-running the installer.
Also, the alerts for the AV and Defense+ are designed to co-operate. If you get an alert for a known piece of malware, it is handled by the AV and you will not get a Defense+ alert. Depending on how you have configured the AV (you can supress the AV alert by setting it to auto-quarantine), it is possible to get NO ALERTS triggered by malware actions that would normally be triggered by Defense+, when the action is intercepted by the AV.
Hope this helps,
Ewen 
Thanks, I decided to install The Anti-Virus and really like it! It doesn’t slow down my PC like Kaspersky did!
Defense + is a great module. I especially like the View Active Process List. If something is running that is suspect or malicious simply click on the process and terminate it or terminate and block it and its gone. I use my own Anti Virus on my Xp install, I use ESET NOD32 ver 3. I use the C.O.M.O.D.O. Anti Virus module on my Vista Home Premium install. I have no performance hits on either machine.
Honestly guys before I install CIS and after I installed it … I didn’t notice any change regarding the performance … and it only consumes 1MB for the user and 5 for the system …> better than ESET V4 which consumes a lot more than that … << all the numbers are estimated and not accurate and depends on your activity , >:-D
regards