Slow Down

New member, hope this is right place for this.
I used Comodo V2 and finally decided to uninstall quite a while back. It slowed everything down. I have an eMachine T3302, XP home version 1250 ram. I installed V3 couple days ago, all appears to be working fine except everything again is slower. With all the problems on the internet I want the protection but wondering if the slowdown is normal. I was running a Kerio sunbelt firewall but decided to go back to Comodo. I also have AVG 7.5 free version, waiting for bug iron out on version 8.0. I also have a2 squared malware protection. I had these on before I switched firewalls with no slow down problems. Again I would rather be better protected and can handle slowdown if it is a normal procedure.